pubmed-mcp-server

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `malformed_id`: An `ids` element does not match the declared `idType` — most often several identifiers packed into one element, which the comma-delimited upstream batch would split into extra records. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities failed on every attempt the retry budget allowed — retries ran out, or the next backoff would overrun the total deadline. `ncbi_rate_limited`: NCBI answered HTTP 429 (too many requests) and the call stopped on it — retries ran out, the next backoff would overrun the total deadline, or the Retry-After NCBI named outlasts the time left or the 30-second backoff cap. `ncbi_deadline_exceeded`: The total NCBI request deadline expired before NCBI answered successfully — mid-request, while queued, or during a retry backoff. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `malformed_id`: An `ids` element does not match the declared `idType` — most often several identifiers packed into one element, which the comma-delimited upstream batch would split into extra records. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found",
-  "malformed_id"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_rate_limited",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found",
+  "malformed_id"
+]

Previous value: -"Machine-readable failure mode. Declared by this tool: `europepmc_unreachable`: Europe PMC failed on every retry attempt — unreachable, an HTTP 404 or 5xx other than a 504 timeout from its search endpoint, or an empty response with no results. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input — an error message such as an empty query, an empty response to a sort with an undocumented field or no asc/desc direction, or an empty response to a pagination cursor on every attempt. `europepmc_disabled`: Europe PMC service is disabled via EUROPEPMC_ENABLED=false. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `europepmc_unreachable`: Europe PMC failed on every retry attempt — unreachable, an HTTP 404 or 5xx other than a 504 timeout from its search endpoint, or an empty response with no results. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input — an error message in place of results, an empty response to a sort with an undocumented field or no asc/desc direction, or a pagination cursor it cannot read (an empty response on the last attempt the retry budget allows, or a second HTTP 503 when the first page of the same query is served). `europepmc_disabled`: Europe PMC service is disabled via EUROPEPMC_ENABLED=false. Other values are possible when a failure originates below the handler."

Previous value: -"Pagination cursor. Use `*` (default) for the first page; pass the previous response's `nextCursorMark` for subsequent pages."New value: +"Pagination cursor. Use `*` (default) for the first page; pass the previous response's `nextCursorMark` verbatim for subsequent pages. A whitespace-only cursor, invisible characters included, is rejected before the request, and a cursor Europe PMC cannot read fails with `europepmc_invalid_input` once a retry of it fails again while the first page of the same query is served."

Previous value: -"Europe PMC search query. Supports field tokens like `AUTH:\"<name>\"`, `JOURNAL:\"<title>\"`, `TITLE:\"<words>\"`, `PUB_YEAR:[2020 TO 2024]`, `DOI:\"...\"`, `EXT_ID:<pmid> AND SRC:MED`, `PMCID:PMC<digits>`. Identifier tokens may be quoted or unquoted — this tool wraps every query with its `sources` filter, and Europe PMC honors a quoted identifier inside that wrapper. A PubMed-indexed article resolves under `SRC:MED`, not `SRC:PMC`, whichever identifier is used. Free text is matched broadly across abstract/title/keywords."New value: +"Europe PMC search query. Supports field tokens like `AUTH:\"<name>\"`, `JOURNAL:\"<title>\"`, `TITLE:\"<words>\"`, `PUB_YEAR:[2020 TO 2024]`, `DOI:\"...\"`, `EXT_ID:<pmid> AND SRC:MED`, `PMCID:PMC<digits>`. Identifier tokens may be quoted or unquoted — this tool wraps every query with its `sources` filter, and Europe PMC honors a quoted identifier inside that wrapper. A PubMed-indexed article resolves under `SRC:MED`, not `SRC:PMC`, whichever identifier is used. Free text is matched broadly across abstract/title/keywords. A query with no search term — blank once HTML entities are decoded and markup, parentheses, and invisible characters are disregarded, such as `()` or `<b></b>` — is rejected; any other query is sent as written."

Previous value: -"Machine-readable failure mode. Declared by this tool: `europepmc_unreachable`: Europe PMC failed on every retry attempt — unreachable, an HTTP 404 or 5xx other than a 504 timeout from its search endpoint, or an empty response with no results. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input — an error message such as an empty query, an empty response to a sort with an undocumented field or no asc/desc direction, or an empty response to a pagination cursor on every attempt. `europepmc_disabled`: Europe PMC service is disabled via EUROPEPMC_ENABLED=false. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `europepmc_unreachable`: Europe PMC failed on every retry attempt — unreachable, an HTTP 404 or 5xx other than a 504 timeout from its search endpoint, or an empty response with no results. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input — an error message in place of results, an empty response to a sort with an undocumented field or no asc/desc direction, or a pagination cursor it cannot read (an empty response on the last attempt the retry budget allows, or a second HTTP 503 when the first page of the same query is served). `blank_query`: The query contains no search term: nothing is left once whitespace and invisible characters such as a zero-width space are disregarded. pubmed_search_articles and pubmed_europepmc_search first decode HTML entities and also disregard markup and parentheses, so `()`, `<b></b>`, and `&nbsp;` hold no term there; pubmed_search_articles also disregards bracketed field tags such as `[pdat]`. `blank_cursor`: The `cursorMark` holds only whitespace or invisible characters such as a zero-width space. Europe PMC cannot read it and answers with the HTTP 503 it also uses for an outage. `europepmc_disabled`: Europe PMC service is disabled via EUROPEPMC_ENABLED=false. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "europepmc_unreachable",
-  "europepmc_invalid_response",
-  "europepmc_invalid_input",
-  "europepmc_disabled"
-]New value: +[
+  "europepmc_unreachable",
+  "europepmc_invalid_response",
+  "europepmc_invalid_input",
+  "blank_query",
+  "blank_cursor",
+  "europepmc_disabled"
+]

Added value: +{
+  "description": "Records NCBI links to this article — for example retraction notices, errata, expressions of concern, comments, and updates — from `CommentsCorrectionsList`, in NCBI's order and uncapped. `Cites` entries are excluded: they list a bibliography, which `pubmed_find_related` covers with its `references` relationship. Read this alongside `publicationTypes`, not in place of it: that field describes the record itself, and a corrected or questioned article often carries no matching type. Absent when NCBI links nothing other than `Cites` entries, and never set on `book-chapter` or `book` records.",
+  "items": {
+    "additionalProperties": false,
+    "description": "One record NCBI links to this article and published separately from it — for example a retraction notice, erratum, expression of concern, comment, update, or republication.",
+    "properties": {
+      "note": {
+        "description": "NCBI's note on the link, e.g. what an erratum corrected (\"Fuβer, Fabian [corrected to Fußer, Fabian]\"). Absent unless NCBI supplies one.",
+        "type": "string"
+      },
+      "pmid": {
+        "description": "PMID of the linked record — pass it to `pubmed_fetch_articles` to read that record. Absent when the linked record has no PMID, as with many errata.",
+        "type": "string"
+      },
+      "refSource": {
+        "description": "Citation of the linked record as NCBI writes it (e.g. \"Lancet. 2010 Feb 6;375(9713):445. doi: 10.1016/S0140-6736(10)60175-4.\").",
+        "type": "string"
+      },
+      "refType": {
+        "description": "Link type, verbatim from NCBI's `RefType` — e.g. \"RetractionIn\", \"RetractionOf\", \"ErratumIn\", \"ErratumFor\", \"ExpressionOfConcernIn\", \"CommentIn\", \"CommentOn\", \"UpdateIn\". The set is open: treat an unfamiliar value as opaque.",
+        "type": "string"
+      }
+    },
+    "required": [
+      "refType",
+      "refSource"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `invalid_efetch_response`: NCBI EFetch returned a payload missing the PubmedArticleSet wrapper. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities failed on every attempt the retry budget allowed — retries ran out, or the next backoff would overrun the total deadline. `ncbi_rate_limited`: NCBI answered HTTP 429 (too many requests) and the call stopped on it — retries ran out, the next backoff would overrun the total deadline, or the Retry-After NCBI named outlasts the time left or the 30-second backoff cap. `ncbi_deadline_exceeded`: The total NCBI request deadline expired before NCBI answered successfully — mid-request, while queued, or during a retry backoff. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `invalid_efetch_response`: NCBI EFetch returned a payload missing the PubmedArticleSet wrapper. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found",
-  "invalid_efetch_response"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_rate_limited",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found",
+  "invalid_efetch_response"
+]

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities failed on every attempt the retry budget allowed — retries ran out, or the next backoff would overrun the total deadline. `ncbi_rate_limited`: NCBI answered HTTP 429 (too many requests) and the call stopped on it — retries ran out, the next backoff would overrun the total deadline, or the Retry-After NCBI named outlasts the time left or the 30-second backoff cap. `ncbi_deadline_exceeded`: The total NCBI request deadline expired before NCBI answered successfully — mid-request, while queued, or during a retry backoff. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_rate_limited",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found"
+]

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities failed on every attempt the retry budget allowed — retries ran out, or the next backoff would overrun the total deadline. `ncbi_rate_limited`: NCBI answered HTTP 429 (too many requests) and the call stopped on it — retries ran out, the next backoff would overrun the total deadline, or the Retry-After NCBI named outlasts the time left or the 30-second backoff cap. `ncbi_deadline_exceeded`: The total NCBI request deadline expired before NCBI answered successfully — mid-request, while queued, or during a retry backoff. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_rate_limited",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found"
+]

Removed value: -[
-  {
-    "description": "Up to 25 citations, each matched independently.",
-    "items": {
-      "description": "Citation to match against PubMed. Must include at least journal or year — ECitMatch primary-keys on journal+volume+page, so author-only or volume-only inputs guarantee no match.",
-      "properties": {
-        "authorName": {
-          "description": "Author name, typically \"lastname initials\" (e.g., \"mann bj\"). Cannot contain a pipe (\"|\") or a line break.",
-          "pattern": "^[^|\\r\\n]*$",
-          "type": "string"
-        },
-        "firstPage": {
-          "description": "First page number. Cannot contain a pipe (\"|\") or a line break.",
-          "pattern": "^[^|\\r\\n]*$",
-          "type": "string"
-        },
-        "journal": {
-          "description": "Journal title or ISO abbreviation (e.g., \"proc natl acad sci u s a\"). Cannot contain a pipe (\"|\") or a line break.",
-          "pattern": "^[^|\\r\\n]*$",
-          "type": "string"
-        },
-        "key": {
-          "description": "Arbitrary label to track this citation in results. Auto-assigned if omitted. Echoed back unchanged and never sent to NCBI, so any character is accepted here.",
-          "type": "string"
-        },
-        "volume": {
-          "description": "Volume number. Cannot contain a pipe (\"|\") or a line break.",
-          "pattern": "^[^|\\r\\n]*$",
-          "type": "string"
-        },
-        "year": {
-          "description": "Publication year (e.g., \"1991\"). Cannot contain a pipe (\"|\") or a line break.",
-          "pattern": "^[^|\\r\\n]*$",
-          "type": "string"
-        }
-      },
-      "type": "object"
-    },
-    "maxItems": 25,
-    "minItems": 1,
-    "type": "array"
-  },
-  {
-    "description": "Citation to match against PubMed. Must include at least journal or year — ECitMatch primary-keys on journal+volume+page, so author-only or volume-only inputs guarantee no match.",
-    "properties": {
-      "authorName": {
-        "description": "Author name, typically \"lastname initials\" (e.g., \"mann bj\"). Cannot contain a pipe (\"|\") or a line break.",
-        "pattern": "^[^|\\r\\n]*$",
-        "type": "string"
-      },
-      "firstPage": {
-        "description": "First page number. Cannot contain a pipe (\"|\") or a line break.",
-        "pattern": "^[^|\\r\\n]*$",
-        "type": "string"
-      },
-      "journal": {
-        "description": "Journal title or ISO abbreviation (e.g., \"proc natl acad sci u s a\"). Cannot contain a pipe (\"|\") or a line break.",
-        "pattern": "^[^|\\r\\n]*$",
-        "type": "string"
-      },
-      "key": {
-        "description": "Arbitrary label to track this citation in results. Auto-assigned if omitted. Echoed back unchanged and never sent to NCBI, so any character is accepted here.",
-        "type": "string"
-      },
-      "volume": {
-        "description": "Volume number. Cannot contain a pipe (\"|\") or a line break.",
-        "pattern": "^[^|\\r\\n]*$",
-        "type": "string"
-      },
-      "year": {
-        "description": "Publication year (e.g., \"1991\"). Cannot contain a pipe (\"|\") or a line break.",
-        "pattern": "^[^|\\r\\n]*$",
-        "type": "string"
-      }
-    },
-    "type": "object"
-  }
-]

Previous value: -"Citations to look up — an array of up to 25, or a single citation object. More fields = better match accuracy."New value: +"Citations to look up, 1–25, each matched independently. More fields = better match accuracy."

Added value: +{
+  "description": "Citation to match against PubMed. Must include at least journal or year — ECitMatch primary-keys on journal+volume+page, so author-only or volume-only inputs guarantee no match.",
+  "properties": {
+    "authorName": {
+      "description": "Author name, typically \"lastname initials\" (e.g., \"mann bj\"). Cannot contain a pipe (\"|\") or a line break.",
+      "pattern": "^[^|\\r\\n]*$",
+      "type": "string"
+    },
+    "firstPage": {
+      "description": "First page number. Cannot contain a pipe (\"|\") or a line break.",
+      "pattern": "^[^|\\r\\n]*$",
+      "type": "string"
+    },
+    "journal": {
+      "description": "Journal title or ISO abbreviation (e.g., \"proc natl acad sci u s a\"). Cannot contain a pipe (\"|\") or a line break.",
+      "pattern": "^[^|\\r\\n]*$",
+      "type": "string"
+    },
+    "key": {
+      "description": "Arbitrary label to track this citation in results. Auto-assigned if omitted. Echoed back unchanged and never sent to NCBI, so any character is accepted here.",
+      "type": "string"
+    },
+    "volume": {
+      "description": "Volume number. Cannot contain a pipe (\"|\") or a line break.",
+      "pattern": "^[^|\\r\\n]*$",
+      "type": "string"
+    },
+    "year": {
+      "description": "Publication year (e.g., \"1991\"). Cannot contain a pipe (\"|\") or a line break.",
+      "pattern": "^[^|\\r\\n]*$",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

Added value: +25

Added value: +1

Added value: +"array"

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities failed on every attempt the retry budget allowed — retries ran out, or the next backoff would overrun the total deadline. `ncbi_rate_limited`: NCBI answered HTTP 429 (too many requests) and the call stopped on it — retries ran out, the next backoff would overrun the total deadline, or the Retry-After NCBI named outlasts the time left or the 30-second backoff cap. `ncbi_deadline_exceeded`: The total NCBI request deadline expired before NCBI answered successfully — mid-request, while queued, or during a retry backoff. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_rate_limited",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found"
+]

Previous value: -"MeSH descriptor name or free-text term to look up. Must carry a term: a blank or whitespace-only value is rejected rather than searched."New value: +"MeSH descriptor name or free-text term to look up. Must carry a term: a value of only whitespace or invisible characters, such as a zero-width space, is rejected rather than searched."

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and anything the tool strips before searching, are removed — so NCBI would receive a blank term. pubmed_search_articles strips markup, bracketed field tags, and parentheses, so a bare field tag such as `[pdat]` or empty parentheses `()` count as blank there. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities failed on every attempt the retry budget allowed — retries ran out, or the next backoff would overrun the total deadline. `ncbi_rate_limited`: NCBI answered HTTP 429 (too many requests) and the call stopped on it — retries ran out, the next backoff would overrun the total deadline, or the Retry-After NCBI named outlasts the time left or the 30-second backoff cap. `ncbi_deadline_exceeded`: The total NCBI request deadline expired before NCBI answered successfully — mid-request, while queued, or during a retry backoff. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query contains no search term: nothing is left once whitespace and invisible characters such as a zero-width space are disregarded. pubmed_search_articles and pubmed_europepmc_search first decode HTML entities and also disregard markup and parentheses, so `()`, `<b></b>`, and `&nbsp;` hold no term there; pubmed_search_articles also disregards bracketed field tags such as `[pdat]`. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found",
-  "blank_query"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_rate_limited",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found",
+  "blank_query"
+]

Previous value: -"Filter by author name (e.g. \"Smith J\")"New value: +"Filter by author name (e.g. \"Smith J\"). An empty string applies no filter; a value of only whitespace, invisible characters, markup, parentheses, brackets, or double quotes is rejected."

Previous value: -"Filter by date range. The filter is applied only when both `minDate` and `maxDate` are non-empty; either one empty disables the entire date range."New value: +"Filter by date range. The filter is applied only when both `minDate` and `maxDate` are non-empty; either one empty disables the entire date range. A partial date covers its whole year or month, and a range whose `minDate` falls after its `maxDate` is rejected: `2024/06` to `2024` is valid, `2024/07` to `2024/06/30` is not."

Previous value: -"End date (YYYY/MM/DD, YYYY/MM, or YYYY); empty string disables this bound"New value: +"End date (YYYY/MM/DD, YYYY/MM, or YYYY); empty string disables this bound. Must be a real calendar date — `2023/02/29` is rejected."

Previous value: -"Start date (YYYY/MM/DD, YYYY/MM, or YYYY); empty string disables this bound"New value: +"Start date (YYYY/MM/DD, YYYY/MM, or YYYY); empty string disables this bound. Must be a real calendar date — `2023/02/29` is rejected."

Previous value: -"Filter by journal name"New value: +"Filter by journal name. An empty string applies no filter; a value of only whitespace, invisible characters, markup, parentheses, brackets, or double quotes is rejected."

Previous value: -"Filter by language (e.g. \"english\")"New value: +"Filter by language (e.g. \"english\"). An empty string applies no filter; a value of only whitespace, invisible characters, markup, parentheses, brackets, or double quotes is rejected."

Previous value: -"Filter by MeSH terms. Multiple terms are AND'd — all must match."New value: +"Filter by MeSH terms. Multiple terms are AND'd — all must match. Empty strings are skipped; an element of only whitespace, invisible characters, markup, parentheses, brackets, or double quotes is rejected."

Previous value: -"Filter by publication type (e.g. \"Review\", \"Clinical Trial\", \"Meta-Analysis\"). Multiple values are OR'd — any match qualifies."New value: +"Filter by publication type (e.g. \"Review\", \"Clinical Trial\", \"Meta-Analysis\"). Multiple values are OR'd — any match qualifies. Empty strings are skipped; an element of only whitespace, invisible characters, markup, parentheses, brackets, or double quotes is rejected."

Previous value: -"PubMed search query (supports full NCBI syntax). Must carry a search term: a value that is blank once markup, bracketed field tags (`[pdat]`), and parentheses are removed is rejected rather than sent to PubMed as an empty term."New value: +"PubMed search query (supports full NCBI syntax). Must carry a search term: a value that is blank once markup, bracketed field tags (`[pdat]`), parentheses, and invisible characters such as a zero-width space are disregarded is rejected rather than sent to PubMed."

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and anything the tool strips before searching, are removed — so NCBI would receive a blank term. pubmed_search_articles strips markup, bracketed field tags, and parentheses, so a bare field tag such as `[pdat]` or empty parentheses `()` count as blank there. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities failed on every attempt the retry budget allowed — retries ran out, or the next backoff would overrun the total deadline. `ncbi_rate_limited`: NCBI answered HTTP 429 (too many requests) and the call stopped on it — retries ran out, the next backoff would overrun the total deadline, or the Retry-After NCBI named outlasts the time left or the 30-second backoff cap. `ncbi_deadline_exceeded`: The total NCBI request deadline expired before NCBI answered successfully — mid-request, while queued, or during a retry backoff. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query contains no search term: nothing is left once whitespace and invisible characters such as a zero-width space are disregarded. pubmed_search_articles and pubmed_europepmc_search first decode HTML entities and also disregard markup and parentheses, so `()`, `<b></b>`, and `&nbsp;` hold no term there; pubmed_search_articles also disregards bracketed field tags such as `[pdat]`. `invalid_date_range`: A `dateRange` bound is not a real calendar date — a month outside 01–12, day 00, or a day past the end of its month such as `2023/02/29` — or `minDate` falls after `maxDate` once PubMed expands each partial date: `minDate` from the start of its year or month, `maxDate` to the end. `blank_filter`: An `author`, `journal`, or `language` value, or a `publicationTypes` or `meshTerms` element, holds no term once markup is removed and HTML entities are decoded — only whitespace, invisible characters such as a zero-width space, parentheses, brackets, or double quotes are left, as in `()` or `\"\"` — so its field clause would carry no term. An exactly-empty string is not blank here; it sets no filter. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found",
-  "blank_query"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_rate_limited",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found",
+  "blank_query",
+  "invalid_date_range",
+  "blank_filter"
+]

Previous value: -"PubMed search query to spell-check. Must carry a term: a blank or whitespace-only value is rejected rather than sent to ESpell."New value: +"PubMed search query to spell-check. Must carry a term: a value of only whitespace or invisible characters, such as a zero-width space, is rejected rather than sent to ESpell."

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and anything the tool strips before searching, are removed — so NCBI would receive a blank term. pubmed_search_articles strips markup, bracketed field tags, and parentheses, so a bare field tag such as `[pdat]` or empty parentheses `()` count as blank there. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities failed on every attempt the retry budget allowed — retries ran out, or the next backoff would overrun the total deadline. `ncbi_rate_limited`: NCBI answered HTTP 429 (too many requests) and the call stopped on it — retries ran out, the next backoff would overrun the total deadline, or the Retry-After NCBI named outlasts the time left or the 30-second backoff cap. `ncbi_deadline_exceeded`: The total NCBI request deadline expired before NCBI answered successfully — mid-request, while queued, or during a retry backoff. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query contains no search term: nothing is left once whitespace and invisible characters such as a zero-width space are disregarded. pubmed_search_articles and pubmed_europepmc_search first decode HTML entities and also disregard markup and parentheses, so `()`, `<b></b>`, and `&nbsp;` hold no term there; pubmed_search_articles also disregards bracketed field tags such as `[pdat]`. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found",
-  "blank_query"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_rate_limited",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found",
+  "blank_query"
+]

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `malformed_id`: An `ids` element does not match the declared `idType` — most often several identifiers packed into one element, which the comma-delimited upstream batch would split into extra records. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `malformed_id`: An `ids` element does not match the declared `idType` — most often several identifiers packed into one element, which the comma-delimited upstream batch would split into extra records. Other values are possible when a failure originates below the handler."

Previous value: -"Machine-readable failure mode. Declared by this tool: `europepmc_unreachable`: Europe PMC was unreachable after all retry attempts. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input (empty query, unknown sort field, malformed parameter). `europepmc_disabled`: Europe PMC service is disabled via EUROPEPMC_ENABLED=false. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `europepmc_unreachable`: Europe PMC failed on every retry attempt — unreachable, an HTTP 404 or 5xx other than a 504 timeout from its search endpoint, or an empty response with no results. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input — an error message such as an empty query, an empty response to a sort with an undocumented field or no asc/desc direction, or an empty response to a pagination cursor on every attempt. `europepmc_disabled`: Europe PMC service is disabled via EUROPEPMC_ENABLED=false. Other values are possible when a failure originates below the handler."

Previous value: -"Europe PMC search query. Supports field tokens like `AUTH:\"<name>\"`, `JOURNAL:\"<title>\"`, `TITLE:\"<words>\"`, `PUB_YEAR:[2020 TO 2024]`, `DOI:\"...\"`, `EXT_ID:<pmid> AND SRC:MED`, `PMCID:PMC<digits>`. Identifier tokens combined with `AND SRC:` must be unquoted — the quoted form matches nothing. Free text is matched broadly across abstract/title/keywords."New value: +"Europe PMC search query. Supports field tokens like `AUTH:\"<name>\"`, `JOURNAL:\"<title>\"`, `TITLE:\"<words>\"`, `PUB_YEAR:[2020 TO 2024]`, `DOI:\"...\"`, `EXT_ID:<pmid> AND SRC:MED`, `PMCID:PMC<digits>`. Identifier tokens may be quoted or unquoted — this tool wraps every query with its `sources` filter, and Europe PMC honors a quoted identifier inside that wrapper. A PubMed-indexed article resolves under `SRC:MED`, not `SRC:PMC`, whichever identifier is used. Free text is matched broadly across abstract/title/keywords."

Previous value: -"Optional EPMC sort: `<field> asc|desc`. Documented sortable fields: `P_PDATE_D` (publication date), `CITED` (citation count), `AUTH_FIRST` (first author surname), `PUB_YEAR` (publication year). Examples: `P_PDATE_D desc` (newest first), `CITED desc` (most cited). Omit for relevance ranking. Fields outside the documented set are rejected by EPMC. Note: `P_PDATE_D` is ignored for preprint-only (`sources: [\"PPR\"]`) result sets — preprints have no populated publication date, so use `PUB_YEAR` to order preprints by date."New value: +"Optional EPMC sort: `<field> asc|desc`, or several comma-separated keys applied in order (`PUB_YEAR desc, CITED desc`). Documented sortable fields: `P_PDATE_D` (publication date), `CITED` (citation count), `AUTH_FIRST` (first author surname), `PUB_YEAR` (publication year). Examples: `P_PDATE_D desc` (newest first), `CITED desc` (most cited). Omit for relevance ranking. Field and direction match case-insensitively. A field outside the documented set may be honored, silently ignored, or rejected, and a sort using one — or a key without `asc`/`desc` — can fail with `europepmc_invalid_input` naming it, even when Europe PMC honors the field. Note: `P_PDATE_D` is ignored for preprint-only (`sources: [\"PPR\"]`) result sets — preprints have no populated publication date, so use `PUB_YEAR` to order preprints by date."

Previous value: -[
-  {
-    "not": {
-      "required": [
-        "error"
-      ]
-    },
-    "required": [
-      "hits",
-      "cursorMark",
-      "searchUrl",
-      "query",
-      "totalCount",
-      "appliedSources"
-    ]
-  },
-  {
-    "required": [
-      "error"
-    ]
-  }
-]New value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "hits",
+      "cursorMark",
+      "searchUrl",
+      "totalCount",
+      "query",
+      "appliedSources"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Previous value: -"Machine-readable failure mode. Declared by this tool: `europepmc_unreachable`: Europe PMC was unreachable after all retry attempts. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input (empty query, unknown sort field, malformed parameter). `europepmc_disabled`: Europe PMC service is disabled via EUROPEPMC_ENABLED=false. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `europepmc_unreachable`: Europe PMC failed on every retry attempt — unreachable, an HTTP 404 or 5xx other than a 504 timeout from its search endpoint, or an empty response with no results. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input — an error message such as an empty query, an empty response to a sort with an undocumented field or no asc/desc direction, or an empty response to a pagination cursor on every attempt. `europepmc_disabled`: Europe PMC service is disabled via EUROPEPMC_ENABLED=false. Other values are possible when a failure originates below the handler."

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `invalid_efetch_response`: NCBI EFetch returned a payload missing the PubmedArticleSet wrapper. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `invalid_efetch_response`: NCBI EFetch returned a payload missing the PubmedArticleSet wrapper. Other values are possible when a failure originates below the handler."

Previous value: -"Per-article budget for body text, in characters. Counts `source=pmc` section and subsection text — which carries the inline blocks the parser renders in place, such as lists, definition lists, block quotes, boxed text, preformatted blocks and displayed formulae — plus table label, caption, cell and footnote text and asset label, caption and `href` text; or the `source=unpaywall` `content` body. Titles, abstracts, identifiers, and references are never counted or shortened. The counted unit is that text alone — the Markdown grid `content[]` renders around the cells (pipes, padding, the divider row, headings) is scaffolding this budget does not measure, so a table renders longer than it costs here. Sections are served first, then tables, then assets, each spending what is left, in document order — admission stops at the first entry that does not fit, and every entry from there on is dropped whole rather than cut mid-row or returned with a shortened caption, counted in `truncation.omittedTables` / `truncation.omittedAssets` and named in `truncation.articles[].omittedTableNames` / `omittedAssetNames`. Applied after `sections`, `maxSections`, `includeReferences`, `includeTables`, and `includeAssets`, so semantic filtering is unaffected. This knob alone bounds only bodies: the response-wide ceiling it implies is this value times the number of articles returned, plus every uncounted field. Use `maxResponseCharacters` for a true whole-response ceiling. Omit for the full body."New value: +"Per-article budget for body text, in characters. Counts `source=pmc` section and subsection text — which carries the inline blocks the parser renders in place, such as lists, definition lists, block quotes, boxed text, preformatted blocks and displayed formulae — plus table label, caption, cell and footnote text and asset label, caption and `href` text; or the `source=unpaywall` `content` body. Titles, abstracts, identifiers, and references are never counted or shortened. Shortened text ends at the last word boundary inside its allowance, so it can come back a few characters under it. The counted unit is that text alone — the Markdown grid `content[]` renders around the cells (pipes, padding, the divider row, headings) is scaffolding this budget does not measure, so a table renders longer than it costs here. Sections are served first, then tables, then assets, each spending what is left, in document order — admission stops at the first entry that does not fit, and every entry from there on is dropped whole rather than cut mid-row or returned with a shortened caption, counted in `truncation.omittedTables` / `truncation.omittedAssets` and named in `truncation.articles[].omittedTableNames` / `omittedAssetNames`. Applied after `sections`, `maxSections`, `includeReferences`, `includeTables`, and `includeAssets`, so semantic filtering is unaffected. This knob alone bounds only bodies: the response-wide ceiling it implies is this value times the number of articles returned, plus every uncounted field. Use `maxResponseCharacters` for a true whole-response ceiling. Omit for the full body."

Previous value: -"How to spend `maxCharacters` across an article that exceeds it. truncate: fill sections in document order, so early sections stay whole and sections past the budget are dropped (counted in `truncation.omittedSections`). outline: split the budget evenly so every section keeps its heading, and an excerpt as far as the budget reaches — use it to survey what an article contains before requesting specific `sections`. Ignored when no budget is set, and identical for `source=unpaywall` bodies, which have no headings to preserve."New value: +"How to spend `maxCharacters` across an article that exceeds it. truncate: fill sections in document order, so early sections stay whole, the section the budget runs out in is cut, and every section or subsection past that point is dropped (counted in `truncation.omittedSections`). outline: split the budget evenly so every section and subsection keeps its heading, and an excerpt as far as the budget reaches — a heading the budget left empty is marked as such in the rendered text. Use it to survey what an article contains before requesting specific `sections`. Ignored when no budget is set, and identical for `source=unpaywall` bodies, which have no headings to preserve."

Previous value: -[
-  {
-    "additionalProperties": false,
-    "description": "Structured JATS full-text article. `viaSource` records whether the JATS came from NCBI PMC or Europe PMC.",
-    "properties": {
-      "abstract": {
-        "description": "Abstract",
-        "type": "string"
-      },
-      "affiliations": {
-        "description": "Author affiliations",
-        "items": {
-          "type": "string"
-        },
-        "type": "array"
-      },
-      "articleType": {
-        "description": "Article type",
-        "type": "string"
-      },
-      "assets": {
-        "description": "Every `<fig>` and `<supplementary-material>` the article carries, in document order — from the body and from `<floats-group>`, `<back>` and appendices alike. Each one lifted from the body leaves a `[Figure: <label>]` or `[Supplementary: <label>]` marker at its position in the section text, so reading order survives the lift. Absent when the article deposits none, when `includeAssets` is false, or when a `sections` filter left none standing.",
-        "items": {
-          "additionalProperties": false,
-          "description": "One figure or supplementary-material item, with its caption, pointer, and section",
-          "properties": {
-            "assetType": {
-              "description": "Which captioned element this came from — `figure` for a `<fig>`, `supplementary-material` for a `<supplementary-material>` deposit",
-              "enum": [
-                "figure",
-                "supplementary-material"
-              ],
-              "type": "string"
-            },
-            "caption": {
-              "description": "Caption text, with the label excluded",
-              "type": "string"
-            },
-            "href": {
-              "description": "The `<graphic>`/`<media>` `@xlink:href` exactly as deposited — a pointer into the PMC deposit (`MOL2-20-1253-g001.jpg`), not a fetchable URL. No absolute form of it resolves; read the rendered article at `pmcUrl` instead. Absent when the deposit names no file.",
-              "type": "string"
-            },
-            "id": {
-              "description": "JATS `id` attribute — the target body-text cross-references point at",
-              "type": "string"
-            },
-            "label": {
-              "description": "Display label as printed, e.g. `Fig. 1`",
-              "type": "string"
-            },
-            "sectionTitle": {
-              "description": "Title of the innermost section enclosing the asset, wherever that section sits — body, `<back>` matter, or an appendix all count. Absent for an asset inside no section at all, such as a `<floats-group>` deposit.",
-              "type": "string"
-            }
-          },
-          "required": [
-            "assetType"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "authors": {
-        "description": "Authors",
-        "items": {
-          "additionalProperties": false,
-          "description": "Author entry",
-          "properties": {
-            "collectiveName": {
-              "description": "Group name",
-              "type": "string"
-            },
-            "givenNames": {
-              "description": "Given names",
-              "type": "string"
-            },
-            "lastName": {
-              "description": "Last name",
-              "type": "string"
-            }
-          },
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "doi": {
-        "description": "DOI, cased as the tier that served this record reports it (NCBI PMC, Europe PMC, or Unpaywall). DOIs are case-insensitive by spec and no case normalization is applied here, so casing can differ between tiers and from other tools — compare case-insensitively.",
-        "type": "string"
-      },
-      "epmcId": {
-        "description": "Europe PMC record id — present when `viaSource` is `europepmc`",
-        "type": "string"
-      },
-      "epmcSource": {
-        "description": "Europe PMC source code when `viaSource` is `europepmc`. Common values: `MED` (PubMed-derived), `PMC` (PMC counterpart), `PPR` (preprint), `PAT` (patent), `AGR` (Agricola), plus less common codes (`CTX`, `CBA`, `ETH`, `HIR`). Treat as opaque — EPMC may introduce new codes.",
-        "type": "string"
-      },
-      "journal": {
-        "additionalProperties": false,
-        "description": "Journal information",
-        "properties": {
-          "elocationId": {
-            "description": "Electronic article locator from JATS `<elocation-id>` — the publisher-assigned article number (e.g. \"e20542\"). Journals that assign article numbers deposit no `<fpage>`, so this is the only locator on roughly half of PMC records. Never a substitute for `pages`; JATS carries no type attribute, so there is no counterpart to the `elocationIdType` that `pubmed_fetch_articles` reports.",
-            "type": "string"
-          },
-          "issn": {
-            "description": "ISSN",
-            "type": "string"
-          },
-          "issue": {
-            "description": "Issue number",
-            "type": "string"
-          },
-          "pages": {
-            "description": "Page range",
-            "type": "string"
-          },
-          "title": {
-            "description": "Journal title",
-            "type": "string"
-          },
-          "volume": {
-            "description": "Volume number",
-            "type": "string"
-          }
-        },
-        "type": "object"
-      },
-      "keywords": {
-        "description": "Keywords",
-        "items": {
-          "type": "string"
-        },
-        "type": "array"
-      },
-      "pmcId": {
-        "description": "PMC ID — present for NCBI PMC records and Europe PMC entries that have a PMC counterpart. Absent for EPMC-only records like preprints; use `epmcId` in that case.",
-        "type": "string"
-      },
-      "pmcUrl": {
-        "description": "PMC URL — derived from `pmcId` when present",
-        "type": "string"
-      },
-      "pmid": {
-        "description": "PubMed ID",
-        "type": "string"
-      },
-      "publicationDate": {
-        "additionalProperties": false,
-        "description": "Publication date",
-        "properties": {
-          "day": {
-            "description": "Publication day",
-            "type": "string"
-          },
-          "month": {
-            "description": "Publication month",
-            "type": "string"
-          },
-          "year": {
-            "description": "Publication year",
-            "type": "string"
-          }
-        },
-        "type": "object"
-      },
-      "pubmedUrl": {
-        "description": "PubMed URL",
-        "type": "string"
-      },
-      "references": {
-        "description": "Reference list",
-        "items": {
-          "additionalProperties": false,
-          "description": "Reference entry",
-          "properties": {
-            "citation": {
-              "description": "Citation text",
-              "type": "string"
-            },
-            "id": {
-              "description": "Reference ID",
-              "type": "string"
-            },
-            "label": {
-              "description": "Reference label",
-              "type": "string"
-            }
-          },
-          "required": [
-            "citation"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "sections": {
-        "description": "Article body sections",
-        "items": {
-          "additionalProperties": false,
-          "description": "Article body section",
-          "properties": {
-            "label": {
-              "description": "Section label",
-              "type": "string"
-            },
-            "subsections": {
-              "description": "Nested subsections",
-              "items": {
-                "additionalProperties": false,
-                "description": "Article subsection",
-                "properties": {
-                  "label": {
-                    "description": "Subsection label",
-                    "type": "string"
-                  },
-                  "text": {
-                    "description": "Subsection body text. Sections nested deeper than this level are folded in here in document order, each heading rendered on its own line above its text.",
-                    "type": "string"
-                  },
-                  "title": {
-                    "description": "Subsection heading",
-                    "type": "string"
-                  }
-                },
-                "required": [
-                  "text"
-                ],
-                "type": "object"
-              },
-              "type": "array"
-            },
-            "text": {
-              "description": "Section body text",
-              "type": "string"
-            },
-            "title": {
-              "description": "Section heading",
-              "type": "string"
-            }
-          },
-          "required": [
-            "text"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "source": {
-        "const": "pmc",
-        "description": "Structured JATS — same DTD whether sourced from NCBI PMC or Europe PMC",
-        "type": "string"
-      },
-      "tables": {
-        "description": "Every `<table-wrap>` the article carries, in document order — from the body and from `<floats-group>`, `<back>` and appendices alike. Absent when the article deposits none, when `includeTables` is false, or when a `sections` filter left none standing.",
-        "items": {
-          "additionalProperties": false,
-          "description": "One table from the article, with its cells, caption, and owning section",
-          "properties": {
-            "caption": {
-              "description": "Caption text, with the label excluded",
-              "type": "string"
-            },
-            "footnotes": {
-              "description": "`<table-wrap-foot>` text, flattened to one string",
-              "type": "string"
-            },
-            "headerRowCount": {
-              "description": "How many leading `rows` entries are header rows — a `<thead>` block, or leading rows made entirely of `<th>`. 0 when the table declares none. Several header rows stack: read one column top to bottom for its full header path.",
-              "type": "number"
-            },
-            "id": {
-              "description": "JATS `id` attribute — the target body-text cross-references point at",
-              "type": "string"
-            },
-            "label": {
-              "description": "Table label as printed, e.g. `TABLE 1`",
-              "type": "string"
-            },
-            "rows": {
-              "description": "Cell text by row, in document order, one entry per grid column. `colspan` and `rowspan` are expanded, so a cell covering several columns or rows repeats its text across each cell it covers and a well-formed table is rectangular — align on position from the left, and read a repeated value as one spanning cell rather than several measurements. Empty when `unextractableReason` is set.",
-              "items": {
-                "description": "One row, as cell text by grid column",
-                "items": {
-                  "type": "string"
-                },
-                "type": "array"
-              },
-              "type": "array"
-            },
-            "sectionTitle": {
-              "description": "Title of the innermost section enclosing the table, wherever that section sits — body, `<back>` matter, or an appendix all count, and in back matter the section name is the only positional cue there is. Absent only for a table inside no section at all, such as a `<floats-group>` deposit.",
-              "type": "string"
-            },
-            "unextractableReason": {
-              "description": "Why `rows` is empty — set only then. graphic-only: the table was deposited as an image with no underlying markup. cals-tgroup: the table uses the CALS `<tgroup>` model, which this server does not extract (0 of 283 tables in an open-access survey used it). no-rows: the markup carried no rows. The label and caption are still returned, so a table that could not be read is visible rather than silently missing.",
-              "enum": [
-                "cals-tgroup",
-                "graphic-only",
-                "no-rows"
-              ],
-              "type": "string"
-            }
-          },
-          "required": [
-            "headerRowCount",
-            "rows"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "title": {
-        "description": "Article title",
-        "type": "string"
-      },
-      "viaSource": {
-        "description": "Which layer produced the JATS: `pmc` for NCBI PMC EFetch (db=pmc), `europepmc` for Europe PMC `fullTextXML`. Both paths return the same JATS shape; the discriminator records origin for observability and license attribution.",
-        "enum": [
-          "pmc",
-          "europepmc"
-        ],
-        "type": "string"
-      }
-    },
-    "required": [
-      "source",
-      "viaSource",
-      "sections"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "description": "Best-effort full text from an open-access copy",
-    "properties": {
-      "content": {
-        "description": "Full article text — Markdown or plain text per `contentFormat`",
-        "type": "string"
-      },
-      "contentFormat": {
-        "description": "How `content` was extracted. html-markdown: Defuddle extracted Markdown from an HTML landing page; light section structure may survive but is not guaranteed. pdf-text: unpdf extracted plain text from a PDF; no section, reference, or heading structure.",
-        "enum": [
-          "html-markdown",
-          "pdf-text"
-        ],
-        "type": "string"
-      },
-      "doi": {
-        "description": "DOI used to locate the open-access copy",
-        "type": "string"
-      },
-      "hostType": {
-        "description": "`publisher` or `repository` — where the OA copy is hosted",
-        "type": "string"
-      },
-      "license": {
-        "description": "License identifier from Unpaywall (e.g. cc-by, cc0)",
-        "type": "string"
-      },
-      "pmcId": {
-        "description": "PMC ID this article was requested under, in `PMC<digits>` form — present for `pmcids` input, absent for `pmids` and `dois` input. Ties the article back to the requested identifier, which `unavailable[]` keys on for the ids that found nothing.",
-        "type": "string"
-      },
-      "pmid": {
-        "description": "PubMed ID when input was `pmids`; absent for `pmcids` and `dois` input",
-        "type": "string"
-      },
-      "pubmedUrl": {
-        "description": "PubMed URL — present when `pmid` is set",
-        "type": "string"
-      },
-      "source": {
-        "const": "unpaywall",
-        "description": "Content fetched from an open-access copy indexed by Unpaywall. Best-effort — structural fidelity depends on `contentFormat`.",
-        "type": "string"
-      },
-      "sourceUrl": {
-        "description": "URL the content was fetched from",
-        "type": "string"
-      },
-      "title": {
-        "description": "Detected article title when present",
-        "type": "string"
-      },
-      "totalPages": {
-        "description": "Page count reported by the PDF extractor; absent for HTML",
-        "type": "number"
-      },
-      "version": {
-        "description": "OA version: submittedVersion | acceptedVersion | publishedVersion",
-        "type": "string"
-      },
-      "viaSource": {
-        "const": "unpaywall",
-        "description": "Layer that produced this article. Constant `unpaywall` for this branch.",
-        "type": "string"
-      },
-      "wordCount": {
-        "description": "Approximate word count reported by the HTML extractor; absent for PDFs",
-        "type": "number"
-      }
-    },
-    "required": [
-      "source",
-      "viaSource",
-      "contentFormat",
-      "doi",
-      "sourceUrl",
-      "content"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "description": "Structured JATS full-text article. `viaSource` records whether the JATS came from NCBI PMC or Europe PMC.",
+    "properties": {
+      "abstract": {
+        "description": "Abstract",
+        "type": "string"
+      },
+      "affiliations": {
+        "description": "Author affiliations",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "articleType": {
+        "description": "Article type",
+        "type": "string"
+      },
+      "assets": {
+        "description": "Every `<fig>` and `<supplementary-material>` the article carries, in document order — from the body and from `<floats-group>`, `<back>` and appendices alike. Each one lifted from the body leaves a `[Figure: <label>]` or `[Supplementary: <label>]` marker at its position in the section text, so reading order survives the lift. Absent when the article deposits none, when `includeAssets` is false, or when a `sections` filter left none standing.",
+        "items": {
+          "additionalProperties": false,
+          "description": "One figure or supplementary-material item, with its caption, pointer, and section",
+          "properties": {
+            "assetType": {
+              "description": "Which captioned element this came from — `figure` for a `<fig>`, `supplementary-material` for a `<supplementary-material>` deposit",
+              "enum": [
+                "figure",
+                "supplementary-material"
+              ],
+              "type": "string"
+            },
+            "caption": {
+              "description": "Caption text, with the label excluded",
+              "type": "string"
+            },
+            "href": {
+              "description": "The `<graphic>`/`<media>` `@xlink:href` exactly as deposited — a pointer into the PMC deposit (`MOL2-20-1253-g001.jpg`), not a fetchable URL. No absolute form of it resolves; read the rendered article at `pmcUrl` instead. Absent when the deposit names no file.",
+              "type": "string"
+            },
+            "id": {
+              "description": "JATS `id` attribute — the target body-text cross-references point at",
+              "type": "string"
+            },
+            "label": {
+              "description": "Display label as printed, e.g. `Fig. 1`",
+              "type": "string"
+            },
+            "sectionTitle": {
+              "description": "Title of the innermost section enclosing the asset, wherever that section sits — body, `<back>` matter, or an appendix all count. Absent for an asset inside no section at all, such as a `<floats-group>` deposit.",
+              "type": "string"
+            }
+          },
+          "required": [
+            "assetType"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "authors": {
+        "description": "Authors",
+        "items": {
+          "additionalProperties": false,
+          "description": "Author entry",
+          "properties": {
+            "collectiveName": {
+              "description": "Group name",
+              "type": "string"
+            },
+            "givenNames": {
+              "description": "Given names",
+              "type": "string"
+            },
+            "lastName": {
+              "description": "Last name",
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "doi": {
+        "description": "DOI, cased as the tier that served this record reports it (NCBI PMC, Europe PMC, or Unpaywall). DOIs are case-insensitive by spec and no case normalization is applied here, so casing can differ between tiers and from other tools — compare case-insensitively.",
+        "type": "string"
+      },
+      "epmcId": {
+        "description": "Europe PMC record id — present when `viaSource` is `europepmc`",
+        "type": "string"
+      },
+      "epmcSource": {
+        "description": "Europe PMC source code when `viaSource` is `europepmc`. Common values: `MED` (PubMed-derived), `PMC` (PMC counterpart), `PPR` (preprint), `PAT` (patent), `AGR` (Agricola), plus less common codes (`CTX`, `CBA`, `ETH`, `HIR`). Treat as opaque — EPMC may introduce new codes.",
+        "type": "string"
+      },
+      "journal": {
+        "additionalProperties": false,
+        "description": "Journal information",
+        "properties": {
+          "elocationId": {
+            "description": "Electronic article locator from JATS `<elocation-id>` — the publisher-assigned article number (e.g. \"e20542\"). Journals that assign article numbers deposit no `<fpage>`, so this is the only locator on roughly half of PMC records. Never a substitute for `pages`; JATS carries no type attribute, so there is no counterpart to the `elocationIdType` that `pubmed_fetch_articles` reports.",
+            "type": "string"
+          },
+          "issn": {
+            "description": "ISSN",
+            "type": "string"
+          },
+          "issue": {
+            "description": "Issue number",
+            "type": "string"
+          },
+          "pages": {
+            "description": "Page range",
+            "type": "string"
+          },
+          "title": {
+            "description": "Journal title",
+            "type": "string"
+          },
+          "volume": {
+            "description": "Volume number",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "keywords": {
+        "description": "Keywords",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "pmcId": {
+        "description": "PMC ID — present for NCBI PMC records and Europe PMC entries that have a PMC counterpart. Absent for EPMC-only records like preprints; use `epmcId` in that case.",
+        "type": "string"
+      },
+      "pmcUrl": {
+        "description": "PMC URL — derived from `pmcId` when present",
+        "type": "string"
+      },
+      "pmid": {
+        "description": "PubMed ID",
+        "type": "string"
+      },
+      "publicationDate": {
+        "additionalProperties": false,
+        "description": "Publication date",
+        "properties": {
+          "day": {
+            "description": "Publication day",
+            "type": "string"
+          },
+          "month": {
+            "description": "Publication month",
+            "type": "string"
+          },
+          "year": {
+            "description": "Publication year",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "pubmedUrl": {
+        "description": "PubMed URL",
+        "type": "string"
+      },
+      "references": {
+        "description": "Reference list",
+        "items": {
+          "additionalProperties": false,
+          "description": "Reference entry",
+          "properties": {
+            "citation": {
+              "description": "Citation text",
+              "type": "string"
+            },
+            "id": {
+              "description": "Reference ID",
+              "type": "string"
+            },
+            "label": {
+              "description": "Reference label",
+              "type": "string"
+            }
+          },
+          "required": [
+            "citation"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "sections": {
+        "description": "Article body sections",
+        "items": {
+          "additionalProperties": false,
+          "description": "Article body section",
+          "properties": {
+            "label": {
+              "description": "Section label",
+              "type": "string"
+            },
+            "subsections": {
+              "description": "Nested subsections",
+              "items": {
+                "additionalProperties": false,
+                "description": "Article subsection",
+                "properties": {
+                  "label": {
+                    "description": "Subsection label",
+                    "type": "string"
+                  },
+                  "text": {
+                    "description": "Subsection body text. Sections nested deeper than this level are folded in here in document order, each heading rendered on its own line above its text.",
+                    "type": "string"
+                  },
+                  "title": {
+                    "description": "Subsection heading",
+                    "type": "string"
+                  }
+                },
+                "required": [
+                  "text"
+                ],
+                "type": "object"
+              },
+              "type": "array"
+            },
+            "text": {
+              "description": "Section body text",
+              "type": "string"
+            },
+            "title": {
+              "description": "Section heading",
+              "type": "string"
+            }
+          },
+          "required": [
+            "text"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "source": {
+        "const": "pmc",
+        "description": "Structured JATS — same DTD whether sourced from NCBI PMC or Europe PMC",
+        "type": "string"
+      },
+      "tables": {
+        "description": "Every `<table-wrap>` the article carries, in document order — from the body and from `<floats-group>`, `<back>` and appendices alike. Absent when the article deposits none, when `includeTables` is false, or when a `sections` filter left none standing.",
+        "items": {
+          "additionalProperties": false,
+          "description": "One table from the article, with its cells, caption, and owning section",
+          "properties": {
+            "caption": {
+              "description": "Caption text, with the label excluded",
+              "type": "string"
+            },
+            "footnotes": {
+              "description": "`<table-wrap-foot>` text, flattened to one string",
+              "type": "string"
+            },
+            "headerRowCount": {
+              "description": "How many leading `rows` entries are header rows — a `<thead>` block, or leading rows made entirely of `<th>`. 0 when the table declares none. Several header rows stack: read one column top to bottom for its full header path.",
+              "type": "number"
+            },
+            "id": {
+              "description": "JATS `id` attribute — the target body-text cross-references point at",
+              "type": "string"
+            },
+            "label": {
+              "description": "Table label as printed, e.g. `TABLE 1`",
+              "type": "string"
+            },
+            "rows": {
+              "description": "Cell text by row, in document order, one entry per grid column. `colspan` and `rowspan` are expanded, so a cell covering several columns or rows repeats its text across each cell it covers and a well-formed table is rectangular — align on position from the left, and read a repeated value as one spanning cell rather than several measurements. Empty when `unextractableReason` is set.",
+              "items": {
+                "description": "One row, as cell text by grid column",
+                "items": {
+                  "type": "string"
+                },
+                "type": "array"
+              },
+              "type": "array"
+            },
+            "sectionTitle": {
+              "description": "Title of the innermost section enclosing the table, wherever that section sits — body, `<back>` matter, or an appendix all count, and in back matter the section name is the only positional cue there is. Absent only for a table inside no section at all, such as a `<floats-group>` deposit.",
+              "type": "string"
+            },
+            "unextractableReason": {
+              "description": "Why `rows` is empty — set only then. graphic-only: the table was deposited as an image with no underlying markup. cals-tgroup: the table uses the CALS `<tgroup>` model, which this server does not extract (0 of 283 tables in an open-access survey used it). no-rows: the markup carried no rows. The label and caption are still returned, so a table that could not be read is visible rather than silently missing.",
+              "enum": [
+                "cals-tgroup",
+                "graphic-only",
+                "no-rows"
+              ],
+              "type": "string"
+            }
+          },
+          "required": [
+            "headerRowCount",
+            "rows"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "title": {
+        "description": "Article title",
+        "type": "string"
+      },
+      "viaSource": {
+        "description": "Which layer produced the JATS: `pmc` for NCBI PMC EFetch (db=pmc), `europepmc` for Europe PMC `fullTextXML`. Both paths return the same JATS shape; the discriminator records origin for observability and license attribution.",
+        "enum": [
+          "pmc",
+          "europepmc"
+        ],
+        "type": "string"
+      }
+    },
+    "required": [
+      "source",
+      "viaSource",
+      "sections"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "description": "Best-effort full text from an open-access copy",
+    "properties": {
+      "content": {
+        "description": "Full article text — Markdown or plain text per `contentFormat`",
+        "type": "string"
+      },
+      "contentFormat": {
+        "description": "How `content` was extracted. html-markdown: Defuddle extracted Markdown from an HTML landing page; light section structure may survive but is not guaranteed. pdf-text: unpdf extracted plain text from a PDF; no section, reference, or heading structure.",
+        "enum": [
+          "html-markdown",
+          "pdf-text"
+        ],
+        "type": "string"
+      },
+      "doi": {
+        "description": "DOI used to locate the open-access copy",
+        "type": "string"
+      },
+      "hostType": {
+        "description": "`publisher` or `repository` — where the OA copy is hosted",
+        "type": "string"
+      },
+      "journalName": {
+        "description": "Journal or repository name from Unpaywall's record for the DOI (e.g. `medRxiv` for a medRxiv preprint). Absent when Unpaywall has none.",
+        "type": "string"
+      },
+      "license": {
+        "description": "License identifier from Unpaywall (e.g. cc-by, cc0)",
+        "type": "string"
+      },
+      "pmcId": {
+        "description": "PMC ID this article was requested under, in `PMC<digits>` form — present for `pmcids` input, absent for `pmids` and `dois` input. Ties the article back to the requested identifier, which `unavailable[]` keys on for the ids that found nothing.",
+        "type": "string"
+      },
+      "pmid": {
+        "description": "PubMed ID when input was `pmids`; absent for `pmcids` and `dois` input",
+        "type": "string"
+      },
+      "pubmedUrl": {
+        "description": "PubMed URL — present when `pmid` is set",
+        "type": "string"
+      },
+      "source": {
+        "const": "unpaywall",
+        "description": "Content fetched from an open-access copy indexed by Unpaywall. Best-effort — structural fidelity depends on `contentFormat`.",
+        "type": "string"
+      },
+      "sourceUrl": {
+        "description": "URL the content was fetched from",
+        "type": "string"
+      },
+      "title": {
+        "description": "Article title, from the first source that carries one: Unpaywall's record for the DOI, then the Europe PMC record when the chain searched Europe PMC for this id, then — for `html-markdown` content only — the title detected on the page. Absent when none of them has a title.",
+        "type": "string"
+      },
+      "totalPages": {
+        "description": "Page count reported by the PDF extractor; absent for HTML",
+        "type": "number"
+      },
+      "version": {
+        "description": "OA version: submittedVersion | acceptedVersion | publishedVersion",
+        "type": "string"
+      },
+      "viaSource": {
+        "const": "unpaywall",
+        "description": "Layer that produced this article. Constant `unpaywall` for this branch.",
+        "type": "string"
+      },
+      "wordCount": {
+        "description": "Approximate word count reported by the HTML extractor; absent for PDFs",
+        "type": "number"
+      },
+      "year": {
+        "description": "Publication year from Unpaywall's record for the DOI. Absent when Unpaywall has none.",
+        "type": "number"
+      }
+    },
+    "required": [
+      "source",
+      "viaSource",
+      "contentFormat",
+      "doi",
+      "sourceUrl",
+      "content"
+    ],
+    "type": "object"
+  }
+]

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `unpaywall_unreachable`: Unpaywall was unreachable when resolving a DOI or fetching content. `europepmc_unreachable`: Europe PMC was unreachable after all retry attempts. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input (empty query, unknown sort field, malformed parameter). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found",
-  "unpaywall_unreachable",
-  "europepmc_unreachable",
-  "europepmc_invalid_response",
-  "europepmc_invalid_input"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found"
+]

Previous value: -"Per-section accounting for `source: pmc` articles, in document order, including sections dropped for budget. Absent for `source: unpaywall`, whose body has no section structure."New value: +"Per-section accounting for `source: pmc` articles, in document order, including sections dropped for budget; a shortened section lists its subsections. Absent for `source: unpaywall`, whose body has no section structure."

Added value: +{
+  "description": "Section label as printed (e.g. `2`), when the section carries one",
+  "type": "string"
+}

Previous value: -"Body characters this section carries in the response. Zero means the section was dropped in `truncate` mode, or kept as a heading-only entry in `outline` mode."New value: +"Body characters this section carries in the response. Zero means the section was dropped in `truncate` mode, or kept as a heading-only entry in `outline` mode, marked as such in the rendered text."

Added value: +{
+  "description": "Per-subsection accounting for a shortened section, in document order, including subsections dropped for budget — where inside the section the cut landed. Absent when the section was returned whole or carries no subsections.",
+  "items": {
+    "additionalProperties": false,
+    "description": "Character accounting for one subsection of a shortened section",
+    "properties": {
+      "label": {
+        "description": "Subsection label as printed (e.g. `2.1`), when the subsection carries one",
+        "type": "string"
+      },
+      "originalCharacters": {
+        "description": "Body characters this subsection carried before the budget pass",
+        "type": "number"
+      },
+      "returnedCharacters": {
+        "description": "Body characters this subsection carries in the response. Zero means it was dropped in `truncate` mode and counted in `omittedSections`, or kept as a heading-only entry in `outline` mode, marked as such in the rendered text.",
+        "type": "number"
+      },
+      "title": {
+        "description": "Subsection heading, when the subsection carries one",
+        "type": "string"
+      },
+      "truncated": {
+        "description": "True when the subsection returned fewer characters than it originally carried",
+        "type": "boolean"
+      }
+    },
+    "required": [
+      "originalCharacters",
+      "returnedCharacters",
+      "truncated"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

Previous value: -"Body sections dropped entirely because an article budget was exhausted before reaching them. Always 0 in `outline` mode, which keeps every heading."New value: +"Body sections and subsections dropped entirely because an article budget was exhausted before reaching them. A dropped section counts once, together with its subsections. Always 0 in `outline` mode, which keeps every heading."

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `europepmc_unreachable`: Europe PMC was unreachable after all retry attempts. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input (empty query, unknown sort field, malformed parameter). `openalex_unreachable`: OpenAlex was unreachable after all retry attempts. `openalex_invalid_response`: OpenAlex returned a body that could not be parsed (invalid JSON). `all_providers_failed`: Every provider eligible for the requested relationship failed; none answered. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `all_providers_failed`: Every provider eligible for the requested relationship failed; none answered. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found",
-  "europepmc_unreachable",
-  "europepmc_invalid_response",
-  "europepmc_invalid_input",
-  "openalex_unreachable",
-  "openalex_invalid_response",
-  "all_providers_failed"
-]New value: +[
+  "all_providers_failed"
+]

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."

Added value: +[
+  {
+    "description": "Up to 25 citations, each matched independently.",
+    "items": {
+      "description": "Citation to match against PubMed. Must include at least journal or year — ECitMatch primary-keys on journal+volume+page, so author-only or volume-only inputs guarantee no match.",
+      "properties": {
+        "authorName": {
+          "description": "Author name, typically \"lastname initials\" (e.g., \"mann bj\"). Cannot contain a pipe (\"|\") or a line break.",
+          "pattern": "^[^|\\r\\n]*$",
+          "type": "string"
+        },
+        "firstPage": {
+          "description": "First page number. Cannot contain a pipe (\"|\") or a line break.",
+          "pattern": "^[^|\\r\\n]*$",
+          "type": "string"
+        },
+        "journal": {
+          "description": "Journal title or ISO abbreviation (e.g., \"proc natl acad sci u s a\"). Cannot contain a pipe (\"|\") or a line break.",
+          "pattern": "^[^|\\r\\n]*$",
+          "type": "string"
+        },
+        "key": {
+          "description": "Arbitrary label to track this citation in results. Auto-assigned if omitted. Echoed back unchanged and never sent to NCBI, so any character is accepted here.",
+          "type": "string"
+        },
+        "volume": {
+          "description": "Volume number. Cannot contain a pipe (\"|\") or a line break.",
+          "pattern": "^[^|\\r\\n]*$",
+          "type": "string"
+        },
+        "year": {
+          "description": "Publication year (e.g., \"1991\"). Cannot contain a pipe (\"|\") or a line break.",
+          "pattern": "^[^|\\r\\n]*$",
+          "type": "string"
+        }
+      },
+      "type": "object"
+    },
+    "maxItems": 25,
+    "minItems": 1,
+    "type": "array"
+  },
+  {
+    "description": "Citation to match against PubMed. Must include at least journal or year — ECitMatch primary-keys on journal+volume+page, so author-only or volume-only inputs guarantee no match.",
+    "properties": {
+      "authorName": {
+        "description": "Author name, typically \"lastname initials\" (e.g., \"mann bj\"). Cannot contain a pipe (\"|\") or a line break.",
+        "pattern": "^[^|\\r\\n]*$",
+        "type": "string"
+      },
+      "firstPage": {
+        "description": "First page number. Cannot contain a pipe (\"|\") or a line break.",
+        "pattern": "^[^|\\r\\n]*$",
+        "type": "string"
+      },
+      "journal": {
+        "description": "Journal title or ISO abbreviation (e.g., \"proc natl acad sci u s a\"). Cannot contain a pipe (\"|\") or a line break.",
+        "pattern": "^[^|\\r\\n]*$",
+        "type": "string"
+      },
+      "key": {
+        "description": "Arbitrary label to track this citation in results. Auto-assigned if omitted. Echoed back unchanged and never sent to NCBI, so any character is accepted here.",
+        "type": "string"
+      },
+      "volume": {
+        "description": "Volume number. Cannot contain a pipe (\"|\") or a line break.",
+        "pattern": "^[^|\\r\\n]*$",
+        "type": "string"
+      },
+      "year": {
+        "description": "Publication year (e.g., \"1991\"). Cannot contain a pipe (\"|\") or a line break.",
+        "pattern": "^[^|\\r\\n]*$",
+        "type": "string"
+      }
+    },
+    "type": "object"
+  }
+]

Previous value: -"Citations to look up. More fields = better match accuracy."New value: +"Citations to look up — an array of up to 25, or a single citation object. More fields = better match accuracy."

Removed value: -{
-  "description": "Citation to match against PubMed. Must include at least journal or year — ECitMatch primary-keys on journal+volume+page, so author-only or volume-only inputs guarantee no match.",
-  "properties": {
-    "authorName": {
-      "description": "Author name, typically \"lastname initials\" (e.g., \"mann bj\"). Cannot contain a pipe (\"|\") or a line break.",
-      "pattern": "^[^|\\r\\n]*$",
-      "type": "string"
-    },
-    "firstPage": {
-      "description": "First page number. Cannot contain a pipe (\"|\") or a line break.",
-      "pattern": "^[^|\\r\\n]*$",
-      "type": "string"
-    },
-    "journal": {
-      "description": "Journal title or ISO abbreviation (e.g., \"proc natl acad sci u s a\"). Cannot contain a pipe (\"|\") or a line break.",
-      "pattern": "^[^|\\r\\n]*$",
-      "type": "string"
-    },
-    "key": {
-      "description": "Arbitrary label to track this citation in results. Auto-assigned if omitted. Echoed back unchanged and never sent to NCBI, so any character is accepted here.",
-      "type": "string"
-    },
-    "volume": {
-      "description": "Volume number. Cannot contain a pipe (\"|\") or a line break.",
-      "pattern": "^[^|\\r\\n]*$",
-      "type": "string"
-    },
-    "year": {
-      "description": "Publication year (e.g., \"1991\"). Cannot contain a pipe (\"|\") or a line break.",
-      "pattern": "^[^|\\r\\n]*$",
-      "type": "string"
-    }
-  },
-  "type": "object"
-}

Removed value: -25

Removed value: -1

Removed value: -"array"

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and any markup the tool strips first, are removed — so NCBI would receive a blank term. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and anything the tool strips before searching, are removed — so NCBI would receive a blank term. pubmed_search_articles strips markup, bracketed field tags, and parentheses, so a bare field tag such as `[pdat]` or empty parentheses `()` count as blank there. Other values are possible when a failure originates below the handler."

Previous value: -"PubMed search query (supports full NCBI syntax). Must carry a search term: a value that is blank once markup is stripped is rejected rather than sent to PubMed as an empty term."New value: +"PubMed search query (supports full NCBI syntax). Must carry a search term: a value that is blank once markup, bracketed field tags (`[pdat]`), and parentheses are removed is rejected rather than sent to PubMed as an empty term."

Previous value: -[
-  {
-    "not": {
-      "required": [
-        "error"
-      ]
-    },
-    "required": [
-      "query",
-      "offset",
-      "pmids",
-      "summaries",
-      "searchUrl",
-      "effectiveQuery",
-      "totalCount",
-      "appliedFilters"
-    ]
-  },
-  {
-    "required": [
-      "error"
-    ]
-  }
-]New value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "query",
+      "offset",
+      "pmids",
+      "summaries",
+      "searchUrl",
+      "totalCount",
+      "effectiveQuery",
+      "appliedFilters"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and any markup the tool strips first, are removed — so NCBI would receive a blank term. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and anything the tool strips before searching, are removed — so NCBI would receive a blank term. pubmed_search_articles strips markup, bracketed field tags, and parentheses, so a bare field tag such as `[pdat]` or empty parentheses `()` count as blank there. Other values are possible when a failure originates below the handler."

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and any markup the tool strips first, are removed — so NCBI would receive a blank term. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: The local NCBI request queue shed the call — the queue is full, or the call cannot start before its total deadline (for example behind the cooldown that follows an NCBI 429). `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and anything the tool strips before searching, are removed — so NCBI would receive a blank term. pubmed_search_articles strips markup, bracketed field tags, and parentheses, so a bare field tag such as `[pdat]` or empty parentheses `()` count as blank there. Other values are possible when a failure originates below the handler."

Previous value: -"Article identifiers to convert. All IDs must be the same type. DOIs: \"10.1093/nar/gks1195\", PMIDs: \"23193287\", PMCIDs: \"PMC3531190\" (the \"PMC\" prefix is optional — bare digits like \"3531190\" are also accepted)."New value: +"Article identifiers to convert — one identifier per element, all of the same type. Each element is checked against `idType` before the request: `doi` starts with \"10.\" and carries a \"/\" (\"10.1093/nar/gks1195\"); `pmid` is digits (\"23193287\"); `pmcid` is digits with an optional \"PMC\" prefix (\"PMC3531190\" or \"3531190\"). No element may contain a comma or whitespace — a packed value like \"23193287,37952131\" is rejected, so split it across elements."

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `malformed_id`: An `ids` element does not match the declared `idType` — most often several identifiers packed into one element, which the comma-delimited upstream batch would split into extra records. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found",
+  "malformed_id"
+]

Previous value: -"Author list"New value: +"Author list. On a `book-chapter` these are the chapter's own authors, never the book's editors, which are in `book.editors`. Empty on a Bookshelf record that credits neither."

Added value: +{
+  "additionalProperties": false,
+  "description": "The containing book of a `book-chapter`, or the book itself on a `book` record. Present only on those two record types, and never a stand-in for `journalInfo`.",
+  "properties": {
+    "accession": {
+      "description": "NCBI Bookshelf accession from `ArticleIdList` (`bookaccession`), e.g. \"NBK1247\". The record is readable at `https://www.ncbi.nlm.nih.gov/books/<accession>/`.",
+      "type": "string"
+    },
+    "beginningDate": {
+      "description": "First year of a continuously-updated book, from `Book/BeginningDate` (GeneReviews runs from 1993). Absent on a book published once.",
+      "type": "string"
+    },
+    "collectionTitle": {
+      "description": "Series the book belongs to, from `Book/CollectionTitle` (e.g. \"ADA Clinical Compendia Series\"). Absent for a book outside a series.",
+      "type": "string"
+    },
+    "doi": {
+      "description": "The book's own DOI, from `Book/ELocationID` with `EIdType=\"doi\"`. Distinct from the record-level `doi`, which is the chapter's: a chapter does not inherit this one.",
+      "type": "string"
+    },
+    "edition": {
+      "description": "Edition statement from `Book/Edition`. Rare on Bookshelf titles — absent unless NCBI supplies one.",
+      "type": "string"
+    },
+    "editors": {
+      "description": "Editors of the containing book, from `Book/AuthorList` marked `Type=\"editors\"`. Kept out of `authors`, which carries the chapter's own writers. Absent when the book credits no editors.",
+      "items": {
+        "additionalProperties": false,
+        "description": "One editor of the containing book. Name parts only — editors are a citation credit, not a contributor record, so no affiliations or ORCID are reported for them.",
+        "properties": {
+          "collectiveName": {
+            "description": "Group or committee credited as editor, when the entry names an organization rather than a person. Mutually exclusive with the name-part fields.",
+            "type": "string"
+          },
+          "firstName": {
+            "description": "Editor given name as NCBI supplies it (`ForeName`, often \"Margaret P\"). Absent when NCBI carries initials only, or on a group editor.",
+            "type": "string"
+          },
+          "initials": {
+            "description": "Editor initials with no separators (e.g. \"MP\"). Absent when NCBI supplies none, or on a group editor.",
+            "type": "string"
+          },
+          "lastName": {
+            "description": "Editor surname, from the book's `Book/AuthorList Type=\"editors\"` entry. Absent on a group editor, which carries `collectiveName` instead.",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "endingDate": {
+      "description": "Last year of a closed date range, from `Book/EndingDate`. Absent while a book is still being updated, which leaves the range open-ended.",
+      "type": "string"
+    },
+    "isbns": {
+      "description": "Every `Book/Isbn` on the record. A book commonly carries a print and an electronic ISBN, so this is a list. Absent for a Bookshelf title with no ISBN, which is most of them.",
+      "items": {
+        "description": "One ISBN, verbatim as NCBI reports it — leading zeros intact",
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "medium": {
+      "description": "Medium the book is published in, from `Book/Medium` — \"Internet\" wherever NCBI supplies it. Absent when NCBI supplies none; it is never defaulted.",
+      "type": "string"
+    },
+    "pubDate": {
+      "description": "Publication year from `Book/PubDate`. Year only — NCBI's month and day are not reported, since no citation style uses them for a book.",
+      "type": "string"
+    },
+    "publisher": {
+      "description": "Publisher of the book, from `Book/Publisher/PublisherName`.",
+      "type": "string"
+    },
+    "publisherLocation": {
+      "description": "Place of publication, from `Book/Publisher/PublisherLocation` (e.g. \"Seattle (WA)\"). Absent when NCBI supplies no place.",
+      "type": "string"
+    },
+    "title": {
+      "description": "Title of the containing book, from `Book/BookTitle` (e.g. \"GeneReviews®\"). On a `book` record this is the same value as the record's own `title`.",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

Previous value: -"Journal information"New value: +"Journal information. Present on `journal-article` records only — absent on `book-chapter` and `book` records, because a Bookshelf record has no journal and its book title is never reported as one; read `book` for those. (#114)"

Added value: +{
+  "description": "Electronic article locator from NCBI `ELocationID` — the publisher-assigned article number (e.g. \"2400512\"). Journals that assign article numbers instead of pages often omit pagination entirely, leaving this the only locator. Never a substitute for `pages`, and never the DOI: a DOI-typed `ELocationID` is reported in `doi` instead. Absent when the only locator NCBI supplies is marked invalid.",
+  "type": "string"
+}

Added value: +{
+  "description": "Type of `elocationId`, from NCBI's `EIdType` attribute — \"pii\" in practice. Free-form: NCBI does not close the set, so treat an unfamiliar value as opaque.",
+  "type": "string"
+}

Added value: +{
+  "description": "Which kind of PubMed record this is, set from the XML element it arrived in: `journal-article` for an ordinary article, `book-chapter` for an NCBI Bookshelf chapter, `book` for a whole Bookshelf book. Read this to tell the three apart — `publicationTypes` cannot, because PubMed labels a Bookshelf record \"Review\" or \"Study Guide\". `journalInfo` is present only on `journal-article`; `book` only on the other two.",
+  "enum": [
+    "journal-article",
+    "book-chapter",
+    "book"
+  ],
+  "type": "string"
+}

Previous value: -"Article title"New value: +"Article title — the chapter title on a `book-chapter`, and the book title on a `book` record, where it repeats `book.title`."

Added value: +[
+  "recordType"
+]

Previous value: -"PMIDs that returned no article data. Reported in full regardless of where a `maxResponseCharacters` cutoff lands — these are misses, not deferrals, and re-requesting them returns nothing."New value: +"PMIDs PubMed returned no record for. That is all this reports: PubMed omits an unknown PMID silently, with no error and no reason, so the absence says nothing about whether the PMID exists. Reported in full regardless of where a `maxResponseCharacters` cutoff lands — these are misses, not deferrals. Use `pubmed_search_articles` to find PMIDs that do resolve."

Previous value: -"DOIs to resolve (e.g. [\"10.21203/rs.3.rs-9010375/v1\"]). Provide exactly one of `pmcids`, `pmids`, or `dois`. Resolved to a PMCID via the PMC ID Converter and returned as structured JATS when the article is in PMC; DOIs with no PMC counterpart (preprints, EPMC-only OA) fall through to Europe PMC, then Unpaywall, when those layers are enabled."New value: +"DOIs to resolve (e.g. [\"10.21203/rs.3.rs-9010375/v1\"]), one per element. Provide exactly one of `pmcids`, `pmids`, or `dois`. Resolved to a PMCID via the PMC ID Converter and returned as structured JATS when the article is in PMC; DOIs with no PMC counterpart (preprints, EPMC-only OA) fall through to Europe PMC, then Unpaywall, when those layers are enabled."

Removed value: -3

Added value: +"^10\\.[^\\s,]+\\/[^\\s,]+$"

Added value: +{
+  "default": true,
+  "description": "Include the article's figures and supplementary material — `assets[]`, each with its label, caption, enclosing section and deposit pointer. On by default because it is cheaper than tables: a median asset-bearing article grows about 10%, and the body prose already refers to these by label. Set false to omit them, which also removes the `[Figure: …]` / `[Supplementary: …]` markers from the section text, since without the array they point at nothing. Prose-shaped blocks — lists, definition lists, block quotes, boxed text, preformatted blocks, displayed formulae — are section text rather than assets and this switch never affects them. Applies to `source=pmc` results only.",
+  "type": "boolean"
+}

Added value: +{
+  "default": true,
+  "description": "Include the article's tables — cells, captions, labels and footnotes. On by default because a dropped table takes its numbers with it. Table-dense articles pay for it: rendered tables typically add 12–17% to an article record and can more than double it. Set false to omit them, or cap the cost with `maxCharacters`, which drops tables it cannot fit whole. Applies to `source=pmc` results only.",
+  "type": "boolean"
+}

Previous value: -"Per-article budget for body text, in characters. Counts `source=pmc` section and subsection text, or the `source=unpaywall` `content` body; titles, abstracts, identifiers, and references are never counted or shortened. Applied after `sections`, `maxSections`, and `includeReferences`, so semantic filtering is unaffected. This knob alone bounds only bodies: the response-wide ceiling it implies is this value times the number of articles returned, plus every uncounted field. Use `maxResponseCharacters` for a true whole-response ceiling. Omit for the full body."New value: +"Per-article budget for body text, in characters. Counts `source=pmc` section and subsection text — which carries the inline blocks the parser renders in place, such as lists, definition lists, block quotes, boxed text, preformatted blocks and displayed formulae — plus table label, caption, cell and footnote text and asset label, caption and `href` text; or the `source=unpaywall` `content` body. Titles, abstracts, identifiers, and references are never counted or shortened. The counted unit is that text alone — the Markdown grid `content[]` renders around the cells (pipes, padding, the divider row, headings) is scaffolding this budget does not measure, so a table renders longer than it costs here. Sections are served first, then tables, then assets, each spending what is left, in document order — admission stops at the first entry that does not fit, and every entry from there on is dropped whole rather than cut mid-row or returned with a shortened caption, counted in `truncation.omittedTables` / `truncation.omittedAssets` and named in `truncation.articles[].omittedTableNames` / `omittedAssetNames`. Applied after `sections`, `maxSections`, `includeReferences`, `includeTables`, and `includeAssets`, so semantic filtering is unaffected. This knob alone bounds only bodies: the response-wide ceiling it implies is this value times the number of articles returned, plus every uncounted field. Use `maxResponseCharacters` for a true whole-response ceiling. Omit for the full body."

Previous value: -"Filter to specific sections by title, case-insensitive (e.g. [\"Introduction\", \"Methods\", \"Results\", \"Discussion\"]). Applies to `source=pmc` results only."New value: +"Filter to specific sections by title (e.g. [\"Introduction\", \"Methods\", \"Results\", \"Discussion\"]). A term matches a section or subsection title at any nesting depth, case-insensitively, as a substring — \"resul\" matches \"Results\". A section whose own title matches is returned whole; one kept only because a nested subsection matched keeps its heading as a breadcrumb, with its own text cleared and only the matching branch beneath it. Tables and assets narrow with the filter: one whose section did not survive, or that names no section, is dropped. Applies to `source=pmc` results only."

Previous value: -[
-  {
-    "additionalProperties": false,
-    "description": "Structured JATS full-text article. `viaSource` records whether the JATS came from NCBI PMC or Europe PMC.",
-    "properties": {
-      "abstract": {
-        "description": "Abstract",
-        "type": "string"
-      },
-      "affiliations": {
-        "description": "Author affiliations",
-        "items": {
-          "type": "string"
-        },
-        "type": "array"
-      },
-      "articleType": {
-        "description": "Article type",
-        "type": "string"
-      },
-      "authors": {
-        "description": "Authors",
-        "items": {
-          "additionalProperties": false,
-          "description": "Author entry",
-          "properties": {
-            "collectiveName": {
-              "description": "Group name",
-              "type": "string"
-            },
-            "givenNames": {
-              "description": "Given names",
-              "type": "string"
-            },
-            "lastName": {
-              "description": "Last name",
-              "type": "string"
-            }
-          },
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "doi": {
-        "description": "DOI, cased as the tier that served this record reports it (NCBI PMC, Europe PMC, or Unpaywall). DOIs are case-insensitive by spec and no case normalization is applied here, so casing can differ between tiers and from other tools — compare case-insensitively.",
-        "type": "string"
-      },
-      "epmcId": {
-        "description": "Europe PMC record id — present when `viaSource` is `europepmc`",
-        "type": "string"
-      },
-      "epmcSource": {
-        "description": "Europe PMC source code when `viaSource` is `europepmc`. Common values: `MED` (PubMed-derived), `PMC` (PMC counterpart), `PPR` (preprint), `PAT` (patent), `AGR` (Agricola), plus less common codes (`CTX`, `CBA`, `ETH`, `HIR`). Treat as opaque — EPMC may introduce new codes.",
-        "type": "string"
-      },
-      "journal": {
-        "additionalProperties": false,
-        "description": "Journal information",
-        "properties": {
-          "issn": {
-            "description": "ISSN",
-            "type": "string"
-          },
-          "issue": {
-            "description": "Issue number",
-            "type": "string"
-          },
-          "pages": {
-            "description": "Page range",
-            "type": "string"
-          },
-          "title": {
-            "description": "Journal title",
-            "type": "string"
-          },
-          "volume": {
-            "description": "Volume number",
-            "type": "string"
-          }
-        },
-        "type": "object"
-      },
-      "keywords": {
-        "description": "Keywords",
-        "items": {
-          "type": "string"
-        },
-        "type": "array"
-      },
-      "pmcId": {
-        "description": "PMC ID — present for NCBI PMC records and Europe PMC entries that have a PMC counterpart. Absent for EPMC-only records like preprints; use `epmcId` in that case.",
-        "type": "string"
-      },
-      "pmcUrl": {
-        "description": "PMC URL — derived from `pmcId` when present",
-        "type": "string"
-      },
-      "pmid": {
-        "description": "PubMed ID",
-        "type": "string"
-      },
-      "publicationDate": {
-        "additionalProperties": false,
-        "description": "Publication date",
-        "properties": {
-          "day": {
-            "description": "Publication day",
-            "type": "string"
-          },
-          "month": {
-            "description": "Publication month",
-            "type": "string"
-          },
-          "year": {
-            "description": "Publication year",
-            "type": "string"
-          }
-        },
-        "type": "object"
-      },
-      "pubmedUrl": {
-        "description": "PubMed URL",
-        "type": "string"
-      },
-      "references": {
-        "description": "Reference list",
-        "items": {
-          "additionalProperties": false,
-          "description": "Reference entry",
-          "properties": {
-            "citation": {
-              "description": "Citation text",
-              "type": "string"
-            },
-            "id": {
-              "description": "Reference ID",
-              "type": "string"
-            },
-            "label": {
-              "description": "Reference label",
-              "type": "string"
-            }
-          },
-          "required": [
-            "citation"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "sections": {
-        "description": "Article body sections",
-        "items": {
-          "additionalProperties": false,
-          "description": "Article body section",
-          "properties": {
-            "label": {
-              "description": "Section label",
-              "type": "string"
-            },
-            "subsections": {
-              "description": "Nested subsections",
-              "items": {
-                "additionalProperties": false,
-                "description": "Article subsection",
-                "properties": {
-                  "label": {
-                    "description": "Subsection label",
-                    "type": "string"
-                  },
-                  "text": {
-                    "description": "Subsection body text. Sections nested deeper than this level are folded in here in document order, each heading rendered on its own line above its text.",
-                    "type": "string"
-                  },
-                  "title": {
-                    "description": "Subsection heading",
-                    "type": "string"
-                  }
-                },
-                "required": [
-                  "text"
-                ],
-                "type": "object"
-              },
-              "type": "array"
-            },
-            "text": {
-              "description": "Section body text",
-              "type": "string"
-            },
-            "title": {
-              "description": "Section heading",
-              "type": "string"
-            }
-          },
-          "required": [
-            "text"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "source": {
-        "const": "pmc",
-        "description": "Structured JATS — same DTD whether sourced from NCBI PMC or Europe PMC",
-        "type": "string"
-      },
-      "title": {
-        "description": "Article title",
-        "type": "string"
-      },
-      "viaSource": {
-        "description": "Which layer produced the JATS: `pmc` for NCBI PMC EFetch (db=pmc), `europepmc` for Europe PMC `fullTextXML`. Both paths return the same JATS shape; the discriminator records origin for observability and license attribution.",
-        "enum": [
-          "pmc",
-          "europepmc"
-        ],
-        "type": "string"
-      }
-    },
-    "required": [
-      "source",
-      "viaSource",
-      "sections"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "description": "Best-effort full text from an open-access copy",
-    "properties": {
-      "content": {
-        "description": "Full article text — Markdown or plain text per `contentFormat`",
-        "type": "string"
-      },
-      "contentFormat": {
-        "description": "How `content` was extracted. html-markdown: Defuddle extracted Markdown from an HTML landing page; light section structure may survive but is not guaranteed. pdf-text: unpdf extracted plain text from a PDF; no section, reference, or heading structure.",
-        "enum": [
-          "html-markdown",
-          "pdf-text"
-        ],
-        "type": "string"
-      },
-      "doi": {
-        "description": "DOI used to locate the open-access copy",
-        "type": "string"
-      },
-      "hostType": {
-        "description": "`publisher` or `repository` — where the OA copy is hosted",
-        "type": "string"
-      },
-      "license": {
-        "description": "License identifier from Unpaywall (e.g. cc-by, cc0)",
-        "type": "string"
-      },
-      "pmcId": {
-        "description": "PMC ID this article was requested under, in `PMC<digits>` form — present for `pmcids` input, absent for `pmids` and `dois` input. Ties the article back to the requested identifier, which `unavailable[]` keys on for the ids that found nothing.",
-        "type": "string"
-      },
-      "pmid": {
-        "description": "PubMed ID when input was `pmids`; absent for `pmcids` and `dois` input",
-        "type": "string"
-      },
-      "pubmedUrl": {
-        "description": "PubMed URL — present when `pmid` is set",
-        "type": "string"
-      },
-      "source": {
-        "const": "unpaywall",
-        "description": "Content fetched from an open-access copy indexed by Unpaywall. Best-effort — structural fidelity depends on `contentFormat`.",
-        "type": "string"
-      },
-      "sourceUrl": {
-        "description": "URL the content was fetched from",
-        "type": "string"
-      },
-      "title": {
-        "description": "Detected article title when present",
-        "type": "string"
-      },
-      "totalPages": {
-        "description": "Page count reported by the PDF extractor; absent for HTML",
-        "type": "number"
-      },
-      "version": {
-        "description": "OA version: submittedVersion | acceptedVersion | publishedVersion",
-        "type": "string"
-      },
-      "viaSource": {
-        "const": "unpaywall",
-        "description": "Layer that produced this article. Constant `unpaywall` for this branch.",
-        "type": "string"
-      },
-      "wordCount": {
-        "description": "Approximate word count reported by the HTML extractor; absent for PDFs",
-        "type": "number"
-      }
-    },
-    "required": [
-      "source",
-      "viaSource",
-      "contentFormat",
-      "doi",
-      "sourceUrl",
-      "content"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "description": "Structured JATS full-text article. `viaSource` records whether the JATS came from NCBI PMC or Europe PMC.",
+    "properties": {
+      "abstract": {
+        "description": "Abstract",
+        "type": "string"
+      },
+      "affiliations": {
+        "description": "Author affiliations",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "articleType": {
+        "description": "Article type",
+        "type": "string"
+      },
+      "assets": {
+        "description": "Every `<fig>` and `<supplementary-material>` the article carries, in document order — from the body and from `<floats-group>`, `<back>` and appendices alike. Each one lifted from the body leaves a `[Figure: <label>]` or `[Supplementary: <label>]` marker at its position in the section text, so reading order survives the lift. Absent when the article deposits none, when `includeAssets` is false, or when a `sections` filter left none standing.",
+        "items": {
+          "additionalProperties": false,
+          "description": "One figure or supplementary-material item, with its caption, pointer, and section",
+          "properties": {
+            "assetType": {
+              "description": "Which captioned element this came from — `figure` for a `<fig>`, `supplementary-material` for a `<supplementary-material>` deposit",
+              "enum": [
+                "figure",
+                "supplementary-material"
+              ],
+              "type": "string"
+            },
+            "caption": {
+              "description": "Caption text, with the label excluded",
+              "type": "string"
+            },
+            "href": {
+              "description": "The `<graphic>`/`<media>` `@xlink:href` exactly as deposited — a pointer into the PMC deposit (`MOL2-20-1253-g001.jpg`), not a fetchable URL. No absolute form of it resolves; read the rendered article at `pmcUrl` instead. Absent when the deposit names no file.",
+              "type": "string"
+            },
+            "id": {
+              "description": "JATS `id` attribute — the target body-text cross-references point at",
+              "type": "string"
+            },
+            "label": {
+              "description": "Display label as printed, e.g. `Fig. 1`",
+              "type": "string"
+            },
+            "sectionTitle": {
+              "description": "Title of the innermost section enclosing the asset, wherever that section sits — body, `<back>` matter, or an appendix all count. Absent for an asset inside no section at all, such as a `<floats-group>` deposit.",
+              "type": "string"
+            }
+          },
+          "required": [
+            "assetType"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "authors": {
+        "description": "Authors",
+        "items": {
+          "additionalProperties": false,
+          "description": "Author entry",
+          "properties": {
+            "collectiveName": {
+              "description": "Group name",
+              "type": "string"
+            },
+            "givenNames": {
+              "description": "Given names",
+              "type": "string"
+            },
+            "lastName": {
+              "description": "Last name",
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "doi": {
+        "description": "DOI, cased as the tier that served this record reports it (NCBI PMC, Europe PMC, or Unpaywall). DOIs are case-insensitive by spec and no case normalization is applied here, so casing can differ between tiers and from other tools — compare case-insensitively.",
+        "type": "string"
+      },
+      "epmcId": {
+        "description": "Europe PMC record id — present when `viaSource` is `europepmc`",
+        "type": "string"
+      },
+      "epmcSource": {
+        "description": "Europe PMC source code when `viaSource` is `europepmc`. Common values: `MED` (PubMed-derived), `PMC` (PMC counterpart), `PPR` (preprint), `PAT` (patent), `AGR` (Agricola), plus less common codes (`CTX`, `CBA`, `ETH`, `HIR`). Treat as opaque — EPMC may introduce new codes.",
+        "type": "string"
+      },
+      "journal": {
+        "additionalProperties": false,
+        "description": "Journal information",
+        "properties": {
+          "elocationId": {
+            "description": "Electronic article locator from JATS `<elocation-id>` — the publisher-assigned article number (e.g. \"e20542\"). Journals that assign article numbers deposit no `<fpage>`, so this is the only locator on roughly half of PMC records. Never a substitute for `pages`; JATS carries no type attribute, so there is no counterpart to the `elocationIdType` that `pubmed_fetch_articles` reports.",
+            "type": "string"
+          },
+          "issn": {
+            "description": "ISSN",
+            "type": "string"
+          },
+          "issue": {
+            "description": "Issue number",
+            "type": "string"
+          },
+          "pages": {
+            "description": "Page range",
+            "type": "string"
+          },
+          "title": {
+            "description": "Journal title",
+            "type": "string"
+          },
+          "volume": {
+            "description": "Volume number",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "keywords": {
+        "description": "Keywords",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "pmcId": {
+        "description": "PMC ID — present for NCBI PMC records and Europe PMC entries that have a PMC counterpart. Absent for EPMC-only records like preprints; use `epmcId` in that case.",
+        "type": "string"
+      },
+      "pmcUrl": {
+        "description": "PMC URL — derived from `pmcId` when present",
+        "type": "string"
+      },
+      "pmid": {
+        "description": "PubMed ID",
+        "type": "string"
+      },
+      "publicationDate": {
+        "additionalProperties": false,
+        "description": "Publication date",
+        "properties": {
+          "day": {
+            "description": "Publication day",
+            "type": "string"
+          },
+          "month": {
+            "description": "Publication month",
+            "type": "string"
+          },
+          "year": {
+            "description": "Publication year",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "pubmedUrl": {
+        "description": "PubMed URL",
+        "type": "string"
+      },
+      "references": {
+        "description": "Reference list",
+        "items": {
+          "additionalProperties": false,
+          "description": "Reference entry",
+          "properties": {
+            "citation": {
+              "description": "Citation text",
+              "type": "string"
+            },
+            "id": {
+              "description": "Reference ID",
+              "type": "string"
+            },
+            "label": {
+              "description": "Reference label",
+              "type": "string"
+            }
+          },
+          "required": [
+            "citation"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "sections": {
+        "description": "Article body sections",
+        "items": {
+          "additionalProperties": false,
+          "description": "Article body section",
+          "properties": {
+            "label": {
+              "description": "Section label",
+              "type": "string"
+            },
+            "subsections": {
+              "description": "Nested subsections",
+              "items": {
+                "additionalProperties": false,
+                "description": "Article subsection",
+                "properties": {
+                  "label": {
+                    "description": "Subsection label",
+                    "type": "string"
+                  },
+                  "text": {
+                    "description": "Subsection body text. Sections nested deeper than this level are folded in here in document order, each heading rendered on its own line above its text.",
+                    "type": "string"
+                  },
+                  "title": {
+                    "description": "Subsection heading",
+                    "type": "string"
+                  }
+                },
+                "required": [
+                  "text"
+                ],
+                "type": "object"
+              },
+              "type": "array"
+            },
+            "text": {
+              "description": "Section body text",
+              "type": "string"
+            },
+            "title": {
+              "description": "Section heading",
+              "type": "string"
+            }
+          },
+          "required": [
+            "text"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "source": {
+        "const": "pmc",
+        "description": "Structured JATS — same DTD whether sourced from NCBI PMC or Europe PMC",
+        "type": "string"
+      },
+      "tables": {
+        "description": "Every `<table-wrap>` the article carries, in document order — from the body and from `<floats-group>`, `<back>` and appendices alike. Absent when the article deposits none, when `includeTables` is false, or when a `sections` filter left none standing.",
+        "items": {
+          "additionalProperties": false,
+          "description": "One table from the article, with its cells, caption, and owning section",
+          "properties": {
+            "caption": {
+              "description": "Caption text, with the label excluded",
+              "type": "string"
+            },
+            "footnotes": {
+              "description": "`<table-wrap-foot>` text, flattened to one string",
+              "type": "string"
+            },
+            "headerRowCount": {
+              "description": "How many leading `rows` entries are header rows — a `<thead>` block, or leading rows made entirely of `<th>`. 0 when the table declares none. Several header rows stack: read one column top to bottom for its full header path.",
+              "type": "number"
+            },
+            "id": {
+              "description": "JATS `id` attribute — the target body-text cross-references point at",
+              "type": "string"
+            },
+            "label": {
+              "description": "Table label as printed, e.g. `TABLE 1`",
+              "type": "string"
+            },
+            "rows": {
+              "description": "Cell text by row, in document order, one entry per grid column. `colspan` and `rowspan` are expanded, so a cell covering several columns or rows repeats its text across each cell it covers and a well-formed table is rectangular — align on position from the left, and read a repeated value as one spanning cell rather than several measurements. Empty when `unextractableReason` is set.",
+              "items": {
+                "description": "One row, as cell text by grid column",
+                "items": {
+                  "type": "string"
+                },
+                "type": "array"
+              },
+              "type": "array"
+            },
+            "sectionTitle": {
+              "description": "Title of the innermost section enclosing the table, wherever that section sits — body, `<back>` matter, or an appendix all count, and in back matter the section name is the only positional cue there is. Absent only for a table inside no section at all, such as a `<floats-group>` deposit.",
+              "type": "string"
+            },
+            "unextractableReason": {
+              "description": "Why `rows` is empty — set only then. graphic-only: the table was deposited as an image with no underlying markup. cals-tgroup: the table uses the CALS `<tgroup>` model, which this server does not extract (0 of 283 tables in an open-access survey used it). no-rows: the markup carried no rows. The label and caption are still returned, so a table that could not be read is visible rather than silently missing.",
+              "enum": [
+                "cals-tgroup",
+                "graphic-only",
+                "no-rows"
+              ],
+              "type": "string"
+            }
+          },
+          "required": [
+            "headerRowCount",
+            "rows"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "title": {
+        "description": "Article title",
+        "type": "string"
+      },
+      "viaSource": {
+        "description": "Which layer produced the JATS: `pmc` for NCBI PMC EFetch (db=pmc), `europepmc` for Europe PMC `fullTextXML`. Both paths return the same JATS shape; the discriminator records origin for observability and license attribution.",
+        "enum": [
+          "pmc",
+          "europepmc"
+        ],
+        "type": "string"
+      }
+    },
+    "required": [
+      "source",
+      "viaSource",
+      "sections"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "description": "Best-effort full text from an open-access copy",
+    "properties": {
+      "content": {
+        "description": "Full article text — Markdown or plain text per `contentFormat`",
+        "type": "string"
+      },
+      "contentFormat": {
+        "description": "How `content` was extracted. html-markdown: Defuddle extracted Markdown from an HTML landing page; light section structure may survive but is not guaranteed. pdf-text: unpdf extracted plain text from a PDF; no section, reference, or heading structure.",
+        "enum": [
+          "html-markdown",
+          "pdf-text"
+        ],
+        "type": "string"
+      },
+      "doi": {
+        "description": "DOI used to locate the open-access copy",
+        "type": "string"
+      },
+      "hostType": {
+        "description": "`publisher` or `repository` — where the OA copy is hosted",
+        "type": "string"
+      },
+      "license": {
+        "description": "License identifier from Unpaywall (e.g. cc-by, cc0)",
+        "type": "string"
+      },
+      "pmcId": {
+        "description": "PMC ID this article was requested under, in `PMC<digits>` form — present for `pmcids` input, absent for `pmids` and `dois` input. Ties the article back to the requested identifier, which `unavailable[]` keys on for the ids that found nothing.",
+        "type": "string"
+      },
+      "pmid": {
+        "description": "PubMed ID when input was `pmids`; absent for `pmcids` and `dois` input",
+        "type": "string"
+      },
+      "pubmedUrl": {
+        "description": "PubMed URL — present when `pmid` is set",
+        "type": "string"
+      },
+      "source": {
+        "const": "unpaywall",
+        "description": "Content fetched from an open-access copy indexed by Unpaywall. Best-effort — structural fidelity depends on `contentFormat`.",
+        "type": "string"
+      },
+      "sourceUrl": {
+        "description": "URL the content was fetched from",
+        "type": "string"
+      },
+      "title": {
+        "description": "Detected article title when present",
+        "type": "string"
+      },
+      "totalPages": {
+        "description": "Page count reported by the PDF extractor; absent for HTML",
+        "type": "number"
+      },
+      "version": {
+        "description": "OA version: submittedVersion | acceptedVersion | publishedVersion",
+        "type": "string"
+      },
+      "viaSource": {
+        "const": "unpaywall",
+        "description": "Layer that produced this article. Constant `unpaywall` for this branch.",
+        "type": "string"
+      },
+      "wordCount": {
+        "description": "Approximate word count reported by the HTML extractor; absent for PDFs",
+        "type": "number"
+      }
+    },
+    "required": [
+      "source",
+      "viaSource",
+      "contentFormat",
+      "doi",
+      "sourceUrl",
+      "content"
+    ],
+    "type": "object"
+  }
+]

Previous value: -"Optional guidance for a partial or empty body. A `sections`-filter miss names the requested terms and affected article id(s) and suggests retrying without `sections` or using broader headings. A metadata-only record names the id(s) the chain could retrieve as front matter only and points at `pubmed_fetch_articles` for the abstract. A budgeted response names the characters returned versus carried and points at `truncation`. A response-wide budget that deferred articles names the ids to re-request. Absent when none of those applies."New value: +"Optional guidance for a partial or empty body. A `sections`-filter miss names the requested terms and affected article id(s) and suggests retrying without `sections` or using broader headings. A metadata-only record names the id(s) the chain could retrieve as front matter only and points at `pubmed_fetch_articles` for the abstract. A table returned with no cell values names the affected table(s), the article each came from, and why the cells cannot be recovered. A budgeted response names the characters returned versus carried and points at `truncation`. A response-wide budget that deferred articles names the ids to re-request. Absent when none of those applies."

Added value: +{
+  "description": "The dropped assets by name, in document order — each asset's label, else its `id`, else `asset <n>` for its position in the article. Contiguous for the same reason `omittedTableNames` is: admission stops at the first asset that did not fit rather than skipping ahead to a smaller one. Absent when none were dropped.",
+  "items": {
+    "type": "string"
+  },
+  "type": "array"
+}

Added value: +{
+  "description": "Figures and supplementary items this article dropped whole because the budget left no room once sections and tables were served. An asset is never returned with a truncated caption, so it is either returned complete or counted here. Absent when none were dropped.",
+  "type": "number"
+}

Added value: +{
+  "description": "The dropped tables by name, in document order — each table's label, else its `id`, else `table <n>` for its position in the article. Names the tables a bare count only hints at, the way `deferred.ids` names deferred articles. Every table from the first that did not fit onward is here: admission stops at that table rather than skipping ahead to a smaller one, so these are contiguous. Absent when none were dropped.",
+  "items": {
+    "type": "string"
+  },
+  "type": "array"
+}

Added value: +{
+  "description": "Tables this article dropped whole because the budget left no room for them. A table is never cut mid-row, so it is either returned complete or counted here. Absent when none were dropped.",
+  "type": "number"
+}

Added value: +{
+  "description": "Figures and supplementary items dropped whole across every budgeted article, because the budget left no room once body sections and tables were served. Absent when none were dropped. Re-request the affected articles with a higher `maxCharacters`, or with `sections` narrowed, to receive them.",
+  "type": "number"
+}

Added value: +{
+  "description": "Tables dropped whole across every budgeted article, because the budget left no room once body sections were served. Absent when none were dropped. Re-request the affected articles with a higher `maxCharacters`, or with `sections` narrowed, to receive them.",
+  "type": "number"
+}

Previous value: -"Why no full text was returned — the most specific signal any tier that answered reported. not-found: upstream returned no record for this ID. no-pmc-fallback-disabled: every tier was skipped (`triedTiers` is all `not-attempted`) — typically because EPMC (`EUROPEPMC_ENABLED`) and Unpaywall (`UNPAYWALL_EMAIL`) are not configured. no-epmc-fulltext: EPMC indexed the record but publishes no fullTextXML. no-body: the record was retrieved but carries front matter and abstract only, with no body sections — use `pubmed_fetch_articles` for the metadata. no-doi: no DOI to query Unpaywall. no-oa: Unpaywall has no OA copy. fetch-failed: download failed. parse-failed: extraction empty. service-error: upstream server failure (threw, timed out, or returned malformed data). A reason never means the chain ran to completion — read `unqueriedTiers` for that."New value: +"Why no full text was returned — the most specific signal any tier that answered reported. not-found: upstream returned no record for this ID. no-pmc-fallback-disabled: every tier was skipped (`triedTiers` is all `not-attempted`) — typically because EPMC (`EUROPEPMC_ENABLED`) and Unpaywall (`UNPAYWALL_EMAIL`) are not configured. no-epmc-fulltext: EPMC indexed the record but publishes no fullTextXML. no-body: the record was retrieved but carries front matter and abstract only, with no body sections — use `pubmed_fetch_articles` for the metadata. no-doi: the DOI lookup ran and this record has none, so Unpaywall could not be queried. doi-lookup-failed: the DOI lookup itself errored, so whether a DOI exists is unknown and Unpaywall was never reached — retry the request; unlike no-doi this is a transient failure, not a settled answer. no-oa: Unpaywall has no OA copy. fetch-failed: download failed. parse-failed: extraction empty. service-error: upstream server failure (threw, timed out, or returned malformed data). A reason never means the chain ran to completion — read `unqueriedTiers` for that."

Previous value: -[
-  "not-found",
-  "no-pmc-fallback-disabled",
-  "no-epmc-fulltext",
-  "no-body",
-  "no-doi",
-  "no-oa",
-  "fetch-failed",
-  "parse-failed",
-  "service-error"
-]New value: +[
+  "not-found",
+  "no-pmc-fallback-disabled",
+  "no-epmc-fulltext",
+  "no-body",
+  "no-doi",
+  "doi-lookup-failed",
+  "no-oa",
+  "fetch-failed",
+  "parse-failed",
+  "service-error"
+]

Previous value: -"Per-tier outcome. not-attempted: tier was skipped. miss: tier returned no record. no-fulltext: EPMC indexed the record but publishes no fullTextXML. no-body: the tier returned a record with front matter and abstract but no body sections, so the chain continued. no-doi: no DOI to query Unpaywall. no-oa: Unpaywall reports no open-access copy. fetch-failed: OA copy download failed. parse-failed: extraction produced empty content. service-error: tier service threw."New value: +"Per-tier outcome. not-attempted: tier was skipped. miss: tier returned no record. no-fulltext: EPMC indexed the record but publishes no fullTextXML. no-body: the tier returned a record with front matter and abstract but no body sections, so the chain continued. no-doi: the DOI lookup ran and this record has none, so Unpaywall could not be queried. doi-lookup-failed: the DOI lookup itself errored, so whether a DOI exists is unknown and Unpaywall was never reached — retry the request. no-oa: Unpaywall reports no open-access copy. fetch-failed: OA copy download failed. parse-failed: extraction produced empty content. service-error: tier service threw."

Previous value: -[
-  "not-attempted",
-  "miss",
-  "no-fulltext",
-  "no-body",
-  "no-doi",
-  "no-oa",
-  "fetch-failed",
-  "parse-failed",
-  "service-error"
-]New value: +[
+  "not-attempted",
+  "miss",
+  "no-fulltext",
+  "no-body",
+  "no-doi",
+  "doi-lookup-failed",
+  "no-oa",
+  "fetch-failed",
+  "parse-failed",
+  "service-error"
+]

Previous value: -"Author string"New value: +"Author string — the first three of the record's own authors, then \"et al.\". On an NCBI Bookshelf chapter these are the chapter's authors; the book's editors are in `editors`."

Added value: +{
+  "description": "Title of the book an NCBI Bookshelf record belongs to. Present instead of `source` on a book record; absent on a journal article.",
+  "type": "string"
+}

Added value: +{
+  "description": "What PubMed classifies this record as: \"chapter\" or \"book\" for an NCBI Bookshelf record, \"citation\" for an ordinary journal article. Absent when PubMed supplies none.",
+  "type": "string"
+}

Added value: +{
+  "description": "Editors of the containing book, kept out of `authors` so they cannot displace the record's own authors. Absent on a journal article and on a book that credits no editors.",
+  "items": {
+    "description": "One editor, \"Surname Initials\" as ESummary renders it",
+    "type": "string"
+  },
+  "type": "array"
+}

Added value: +{
+  "description": "Publisher of the book an NCBI Bookshelf record belongs to. Present only on a book record; absent on a journal article.",
+  "type": "string"
+}

Previous value: -"Journal source"New value: +"Journal the article appeared in. Absent on an NCBI Bookshelf record, which has no journal — its venue is in `bookTitle` and `publisherName` instead, and `docType` says which kind of record it is."

Added value: +{
+  "description": "Reference-coverage fallbacks that failed instead of answering, so the reference set is unverified rather than confirmed absent. Absent when every provider consulted answered.",
+  "items": {
+    "additionalProperties": false,
+    "description": "One coverage provider that could not be checked",
+    "properties": {
+      "provider": {
+        "description": "Reference-coverage provider that failed",
+        "enum": [
+          "europepmc",
+          "openalex"
+        ],
+        "type": "string"
+      },
+      "reason": {
+        "description": "Declared failure reason, e.g. europepmc_unreachable or provider_disabled",
+        "type": "string"
+      },
+      "retryable": {
+        "description": "Whether a retry can reach this provider",
+        "type": "boolean"
+      }
+    },
+    "required": [
+      "provider",
+      "reason",
+      "retryable"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

Previous value: -"Guidance when results are empty, a fallback provider answered, offset overshot, or Europe PMC rows were excluded for carrying no PubMed PMID. Absent on a clean NCBI result page."New value: +"Guidance when results are empty, a fallback provider answered, offset overshot, a fallback provider could not be reached, or upstream rows were excluded for carrying no PubMed PMID. Absent on a clean NCBI result page."

Previous value: -"Total related articles found before windowing. A Europe PMC total may shrink to the PubMed-addressable count once a request window covers the whole upstream set, since rows without a PubMed PMID cannot be returned."New value: +"Total related articles found before windowing. A Europe PMC or OpenAlex total may shrink to the PubMed-addressable count once a request window covers the whole upstream set, since rows without a PubMed PMID cannot be returned."

Previous value: -"Requested PMIDs that did not return article metadata"New value: +"PMIDs PubMed returned no record for, so nothing could be cited for them. That is all this reports: PubMed omits a PMID it does not recognize silently, with no error and no reason, so the absence says nothing about whether the PMID exists. Use `pubmed_search_articles` to find PMIDs that do resolve."

Previous value: -"Author name, typically \"lastname initials\" (e.g., \"mann bj\")"New value: +"Author name, typically \"lastname initials\" (e.g., \"mann bj\"). Cannot contain a pipe (\"|\") or a line break."

Added value: +"^[^|\\r\\n]*$"

Previous value: -"First page number"New value: +"First page number. Cannot contain a pipe (\"|\") or a line break."

Added value: +"^[^|\\r\\n]*$"

Previous value: -"Journal title or ISO abbreviation (e.g., \"proc natl acad sci u s a\")"New value: +"Journal title or ISO abbreviation (e.g., \"proc natl acad sci u s a\"). Cannot contain a pipe (\"|\") or a line break."

Added value: +"^[^|\\r\\n]*$"

Previous value: -"Arbitrary label to track this citation in results. Auto-assigned if omitted."New value: +"Arbitrary label to track this citation in results. Auto-assigned if omitted. Echoed back unchanged and never sent to NCBI, so any character is accepted here."

Previous value: -"Volume number"New value: +"Volume number. Cannot contain a pipe (\"|\") or a line break."

Added value: +"^[^|\\r\\n]*$"

Previous value: -"Publication year (e.g., \"1991\")"New value: +"Publication year (e.g., \"1991\"). Cannot contain a pipe (\"|\") or a line break."

Added value: +"^[^|\\r\\n]*$"

Previous value: -"MeSH descriptor name or free-text term to look up"New value: +"MeSH descriptor name or free-text term to look up. Must carry a term: a blank or whitespace-only value is rejected rather than searched."

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and any markup the tool strips first, are removed — so NCBI would receive a blank term. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found",
+  "blank_query"
+]

Previous value: -"PubMed search query (supports full NCBI syntax)"New value: +"PubMed search query (supports full NCBI syntax). Must carry a search term: a value that is blank once markup is stripped is rejected rather than sent to PubMed as an empty term."

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and any markup the tool strips first, are removed — so NCBI would receive a blank term. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found",
+  "blank_query"
+]

Previous value: -"Formatted author string"New value: +"Formatted author string — the first three of the record's own authors, then \"et al.\". On an NCBI Bookshelf chapter these are the chapter's authors; the book's editors are reported separately in `editors`."

Added value: +{
+  "description": "Title of the book an NCBI Bookshelf record belongs to, e.g. \"GeneReviews(®)\". Present instead of `source` on a book record; absent on a journal article.",
+  "type": "string"
+}

Added value: +{
+  "description": "What PubMed classifies this record as: \"chapter\" or \"book\" for an NCBI Bookshelf record, \"citation\" for an ordinary journal article. Absent when PubMed supplies none.",
+  "type": "string"
+}

Added value: +{
+  "description": "Editors of the containing book, kept out of `authors` so they cannot displace the record's own authors. Absent on a journal article and on a book that credits no editors.",
+  "items": {
+    "description": "One editor, \"Surname Initials\" as ESummary renders it",
+    "type": "string"
+  },
+  "type": "array"
+}

Added value: +{
+  "description": "Publisher of the book an NCBI Bookshelf record belongs to. Present only on a book record; absent on a journal article.",
+  "type": "string"
+}

Previous value: -"Journal source"New value: +"Journal the article appeared in. Absent on an NCBI Bookshelf record, which has no journal — its venue is in `bookTitle` and `publisherName` instead, and `docType` says which kind of record it is."

Previous value: -"PubMed search query to spell-check"New value: +"PubMed search query to spell-check. Must carry a term: a blank or whitespace-only value is rejected rather than sent to ESpell."

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `blank_query`: The query holds no search term once whitespace, and any markup the tool strips first, are removed — so NCBI would receive a blank term. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found",
+  "blank_query"
+]

Previous value: -"Formatted author string"New value: +"Formatted author string as display-ready plain text — JATS/HTML markup stripped and HTML entities decoded."

Previous value: -"Journal title"New value: +"Journal title as display-ready plain text — JATS/HTML markup stripped and HTML entities decoded."

Previous value: -"Record title"New value: +"Record title as display-ready plain text — JATS/HTML markup stripped and HTML entities decoded."

Previous value: -"Formatted author string"New value: +"Formatted author string as display-ready plain text — JATS/HTML markup stripped and HTML entities decoded."

Previous value: -"Journal title"New value: +"Journal title as display-ready plain text — JATS/HTML markup stripped and HTML entities decoded."

Previous value: -"Article title"New value: +"Article title as display-ready plain text — JATS/HTML markup stripped and HTML entities decoded."

Added value: +{
+  "description": "Opt-in ceiling for the whole response, in characters. Each article is measured as the JSON record it is returned as — title, abstract, authors, journal, MeSH terms, grants, identifiers, every field it carries. Articles are kept in response order until the next one would cross the ceiling; that article and the rest are deferred whole (never partially populated) and listed in `deferred.ids`. Response envelope fields — counts, `unavailablePmids`, `deferred` itself — are not counted. Omit to return every resolved article.",
+  "maximum": 1000000,
+  "minimum": 1,
+  "type": "integer"
+}

Added value: +{
+  "additionalProperties": false,
+  "description": "Continuation state for articles the whole-response budget withheld. Present only when `maxResponseCharacters` deferred at least one article.",
+  "properties": {
+    "deferredCount": {
+      "description": "Articles that resolved but were withheld to stay under the ceiling",
+      "type": "number"
+    },
+    "ids": {
+      "description": "PMIDs of the deferred articles, in response order. Re-call `pubmed_fetch_articles` with these as `pmids` and the same other inputs to retrieve them. Never contains a PMID from `unavailablePmids`.",
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "maxResponseCharacters": {
+      "description": "The `maxResponseCharacters` ceiling this response was budgeted against",
+      "type": "number"
+    },
+    "nextDeferredCharacters": {
+      "description": "Serialized size of the next deferred article — the first entry in `ids`, where the response stopped. Raise `maxResponseCharacters` to at least this to make progress; a smaller article further down `ids` cannot be reached until this one fits.",
+      "type": "number"
+    },
+    "returnedCharacters": {
+      "description": "Serialized characters the returned article records account for",
+      "type": "number"
+    }
+  },
+  "required": [
+    "maxResponseCharacters",
+    "returnedCharacters",
+    "deferredCount",
+    "ids",
+    "nextDeferredCharacters"
+  ],
+  "type": "object"
+}

Previous value: -"Optional guidance when no articles were returned — points to discovery tools. Absent on successful fetches."New value: +"Optional guidance when no articles were returned — points to discovery tools — or when `maxResponseCharacters` deferred articles, naming how to retrieve them. Absent on successful unbudgeted fetches."

Previous value: -"Number of articles returned"New value: +"Number of articles in this response. Under a `maxResponseCharacters` budget this counts the kept articles only; `deferred.deferredCount` covers the rest."

Added value: +{
+  "description": "True when `maxResponseCharacters` withheld at least one resolved article. Absent when the response carries every article that resolved. The continuation state is in `deferred`.",
+  "type": "boolean"
+}

Previous value: -"PMIDs that returned no article data"New value: +"PMIDs that returned no article data. Reported in full regardless of where a `maxResponseCharacters` cutoff lands — these are misses, not deferrals, and re-requesting them returns nothing."

Previous value: -"Per-article budget for body text, in characters. Counts `source=pmc` section and subsection text, or the `source=unpaywall` `content` body; titles, abstracts, identifiers, and references are never counted or shortened. Applied after `sections`, `maxSections`, and `includeReferences`, so semantic filtering is unaffected. The response-wide ceiling is this value times the number of articles returned. Omit for the full body."New value: +"Per-article budget for body text, in characters. Counts `source=pmc` section and subsection text, or the `source=unpaywall` `content` body; titles, abstracts, identifiers, and references are never counted or shortened. Applied after `sections`, `maxSections`, and `includeReferences`, so semantic filtering is unaffected. This knob alone bounds only bodies: the response-wide ceiling it implies is this value times the number of articles returned, plus every uncounted field. Use `maxResponseCharacters` for a true whole-response ceiling. Omit for the full body."

Added value: +{
+  "description": "Opt-in ceiling for the whole response, in characters — the true response-wide counterpart to the per-article `maxCharacters`. Each article is measured as the JSON record it is returned as, after every filter and the per-article body budget: title, abstract, body sections, references, identifiers, license and source metadata — every field it carries. One ledger covers all tiers, so PMC-, Europe PMC-, and Unpaywall-served articles spend the same budget. Articles are kept in response order until the next one would cross the ceiling; that article and the rest are deferred whole (never partially populated) and listed in `deferred.ids`. Response envelope fields — counts, `unavailable`, `truncation`, `deferred` itself — are not counted. Omit to return every resolved article.",
+  "maximum": 1000000,
+  "minimum": 1,
+  "type": "integer"
+}

Previous value: -[
-  {
-    "additionalProperties": false,
-    "description": "Structured JATS full-text article. `viaSource` records whether the JATS came from NCBI PMC or Europe PMC.",
-    "properties": {
-      "abstract": {
-        "description": "Abstract",
-        "type": "string"
-      },
-      "affiliations": {
-        "description": "Author affiliations",
-        "items": {
-          "type": "string"
-        },
-        "type": "array"
-      },
-      "articleType": {
-        "description": "Article type",
-        "type": "string"
-      },
-      "authors": {
-        "description": "Authors",
-        "items": {
-          "additionalProperties": false,
-          "description": "Author entry",
-          "properties": {
-            "collectiveName": {
-              "description": "Group name",
-              "type": "string"
-            },
-            "givenNames": {
-              "description": "Given names",
-              "type": "string"
-            },
-            "lastName": {
-              "description": "Last name",
-              "type": "string"
-            }
-          },
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "doi": {
-        "description": "DOI, cased as the tier that served this record reports it (NCBI PMC, Europe PMC, or Unpaywall). DOIs are case-insensitive by spec and no case normalization is applied here, so casing can differ between tiers and from other tools — compare case-insensitively.",
-        "type": "string"
-      },
-      "epmcId": {
-        "description": "Europe PMC record id — present when `viaSource` is `europepmc`",
-        "type": "string"
-      },
-      "epmcSource": {
-        "description": "Europe PMC source code when `viaSource` is `europepmc`. Common values: `MED` (PubMed-derived), `PMC` (PMC counterpart), `PPR` (preprint), `PAT` (patent), `AGR` (Agricola), plus less common codes (`CTX`, `CBA`, `ETH`, `HIR`). Treat as opaque — EPMC may introduce new codes.",
-        "type": "string"
-      },
-      "journal": {
-        "additionalProperties": false,
-        "description": "Journal information",
-        "properties": {
-          "issn": {
-            "description": "ISSN",
-            "type": "string"
-          },
-          "issue": {
-            "description": "Issue number",
-            "type": "string"
-          },
-          "pages": {
-            "description": "Page range",
-            "type": "string"
-          },
-          "title": {
-            "description": "Journal title",
-            "type": "string"
-          },
-          "volume": {
-            "description": "Volume number",
-            "type": "string"
-          }
-        },
-        "type": "object"
-      },
-      "keywords": {
-        "description": "Keywords",
-        "items": {
-          "type": "string"
-        },
-        "type": "array"
-      },
-      "pmcId": {
-        "description": "PMC ID — present for NCBI PMC records and Europe PMC entries that have a PMC counterpart. Absent for EPMC-only records like preprints; use `epmcId` in that case.",
-        "type": "string"
-      },
-      "pmcUrl": {
-        "description": "PMC URL — derived from `pmcId` when present",
-        "type": "string"
-      },
-      "pmid": {
-        "description": "PubMed ID",
-        "type": "string"
-      },
-      "publicationDate": {
-        "additionalProperties": false,
-        "description": "Publication date",
-        "properties": {
-          "day": {
-            "description": "Publication day",
-            "type": "string"
-          },
-          "month": {
-            "description": "Publication month",
-            "type": "string"
-          },
-          "year": {
-            "description": "Publication year",
-            "type": "string"
-          }
-        },
-        "type": "object"
-      },
-      "pubmedUrl": {
-        "description": "PubMed URL",
-        "type": "string"
-      },
-      "references": {
-        "description": "Reference list",
-        "items": {
-          "additionalProperties": false,
-          "description": "Reference entry",
-          "properties": {
-            "citation": {
-              "description": "Citation text",
-              "type": "string"
-            },
-            "id": {
-              "description": "Reference ID",
-              "type": "string"
-            },
-            "label": {
-              "description": "Reference label",
-              "type": "string"
-            }
-          },
-          "required": [
-            "citation"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "sections": {
-        "description": "Article body sections",
-        "items": {
-          "additionalProperties": false,
-          "description": "Article body section",
-          "properties": {
-            "label": {
-              "description": "Section label",
-              "type": "string"
-            },
-            "subsections": {
-              "description": "Nested subsections",
-              "items": {
-                "additionalProperties": false,
-                "description": "Article subsection",
-                "properties": {
-                  "label": {
-                    "description": "Subsection label",
-                    "type": "string"
-                  },
-                  "text": {
-                    "description": "Subsection body text",
-                    "type": "string"
-                  },
-                  "title": {
-                    "description": "Subsection heading",
-                    "type": "string"
-                  }
-                },
-                "required": [
-                  "text"
-                ],
-                "type": "object"
-              },
-              "type": "array"
-            },
-            "text": {
-              "description": "Section body text",
-              "type": "string"
-            },
-            "title": {
-              "description": "Section heading",
-              "type": "string"
-            }
-          },
-          "required": [
-            "text"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "source": {
-        "const": "pmc",
-        "description": "Structured JATS — same DTD whether sourced from NCBI PMC or Europe PMC",
-        "type": "string"
-      },
-      "title": {
-        "description": "Article title",
-        "type": "string"
-      },
-      "viaSource": {
-        "description": "Which layer produced the JATS: `pmc` for NCBI PMC EFetch (db=pmc), `europepmc` for Europe PMC `fullTextXML`. Both paths return the same JATS shape; the discriminator records origin for observability and license attribution.",
-        "enum": [
-          "pmc",
-          "europepmc"
-        ],
-        "type": "string"
-      }
-    },
-    "required": [
-      "source",
-      "viaSource",
-      "sections"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "description": "Best-effort full text from an open-access copy",
-    "properties": {
-      "content": {
-        "description": "Full article text — Markdown or plain text per `contentFormat`",
-        "type": "string"
-      },
-      "contentFormat": {
-        "description": "How `content` was extracted. html-markdown: Defuddle extracted Markdown from an HTML landing page; light section structure may survive but is not guaranteed. pdf-text: unpdf extracted plain text from a PDF; no section, reference, or heading structure.",
-        "enum": [
-          "html-markdown",
-          "pdf-text"
-        ],
-        "type": "string"
-      },
-      "doi": {
-        "description": "DOI used to locate the open-access copy",
-        "type": "string"
-      },
-      "hostType": {
-        "description": "`publisher` or `repository` — where the OA copy is hosted",
-        "type": "string"
-      },
-      "license": {
-        "description": "License identifier from Unpaywall (e.g. cc-by, cc0)",
-        "type": "string"
-      },
-      "pmcId": {
-        "description": "PMC ID this article was requested under, in `PMC<digits>` form — present for `pmcids` input, absent for `pmids` and `dois` input. Ties the article back to the requested identifier, which `unavailable[]` keys on for the ids that found nothing.",
-        "type": "string"
-      },
-      "pmid": {
-        "description": "PubMed ID when input was `pmids`; absent for `pmcids` and `dois` input",
-        "type": "string"
-      },
-      "pubmedUrl": {
-        "description": "PubMed URL — present when `pmid` is set",
-        "type": "string"
-      },
-      "source": {
-        "const": "unpaywall",
-        "description": "Content fetched from an open-access copy indexed by Unpaywall. Best-effort — structural fidelity depends on `contentFormat`.",
-        "type": "string"
-      },
-      "sourceUrl": {
-        "description": "URL the content was fetched from",
-        "type": "string"
-      },
-      "title": {
-        "description": "Detected article title when present",
-        "type": "string"
-      },
-      "totalPages": {
-        "description": "Page count reported by the PDF extractor; absent for HTML",
-        "type": "number"
-      },
-      "version": {
-        "description": "OA version: submittedVersion | acceptedVersion | publishedVersion",
-        "type": "string"
-      },
-      "viaSource": {
-        "const": "unpaywall",
-        "description": "Layer that produced this article. Constant `unpaywall` for this branch.",
-        "type": "string"
-      },
-      "wordCount": {
-        "description": "Approximate word count reported by the HTML extractor; absent for PDFs",
-        "type": "number"
-      }
-    },
-    "required": [
-      "source",
-      "viaSource",
-      "contentFormat",
-      "doi",
-      "sourceUrl",
-      "content"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "description": "Structured JATS full-text article. `viaSource` records whether the JATS came from NCBI PMC or Europe PMC.",
+    "properties": {
+      "abstract": {
+        "description": "Abstract",
+        "type": "string"
+      },
+      "affiliations": {
+        "description": "Author affiliations",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "articleType": {
+        "description": "Article type",
+        "type": "string"
+      },
+      "authors": {
+        "description": "Authors",
+        "items": {
+          "additionalProperties": false,
+          "description": "Author entry",
+          "properties": {
+            "collectiveName": {
+              "description": "Group name",
+              "type": "string"
+            },
+            "givenNames": {
+              "description": "Given names",
+              "type": "string"
+            },
+            "lastName": {
+              "description": "Last name",
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "doi": {
+        "description": "DOI, cased as the tier that served this record reports it (NCBI PMC, Europe PMC, or Unpaywall). DOIs are case-insensitive by spec and no case normalization is applied here, so casing can differ between tiers and from other tools — compare case-insensitively.",
+        "type": "string"
+      },
+      "epmcId": {
+        "description": "Europe PMC record id — present when `viaSource` is `europepmc`",
+        "type": "string"
+      },
+      "epmcSource": {
+        "description": "Europe PMC source code when `viaSource` is `europepmc`. Common values: `MED` (PubMed-derived), `PMC` (PMC counterpart), `PPR` (preprint), `PAT` (patent), `AGR` (Agricola), plus less common codes (`CTX`, `CBA`, `ETH`, `HIR`). Treat as opaque — EPMC may introduce new codes.",
+        "type": "string"
+      },
+      "journal": {
+        "additionalProperties": false,
+        "description": "Journal information",
+        "properties": {
+          "issn": {
+            "description": "ISSN",
+            "type": "string"
+          },
+          "issue": {
+            "description": "Issue number",
+            "type": "string"
+          },
+          "pages": {
+            "description": "Page range",
+            "type": "string"
+          },
+          "title": {
+            "description": "Journal title",
+            "type": "string"
+          },
+          "volume": {
+            "description": "Volume number",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "keywords": {
+        "description": "Keywords",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "pmcId": {
+        "description": "PMC ID — present for NCBI PMC records and Europe PMC entries that have a PMC counterpart. Absent for EPMC-only records like preprints; use `epmcId` in that case.",
+        "type": "string"
+      },
+      "pmcUrl": {
+        "description": "PMC URL — derived from `pmcId` when present",
+        "type": "string"
+      },
+      "pmid": {
+        "description": "PubMed ID",
+        "type": "string"
+      },
+      "publicationDate": {
+        "additionalProperties": false,
+        "description": "Publication date",
+        "properties": {
+          "day": {
+            "description": "Publication day",
+            "type": "string"
+          },
+          "month": {
+            "description": "Publication month",
+            "type": "string"
+          },
+          "year": {
+            "description": "Publication year",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "pubmedUrl": {
+        "description": "PubMed URL",
+        "type": "string"
+      },
+      "references": {
+        "description": "Reference list",
+        "items": {
+          "additionalProperties": false,
+          "description": "Reference entry",
+          "properties": {
+            "citation": {
+              "description": "Citation text",
+              "type": "string"
+            },
+            "id": {
+              "description": "Reference ID",
+              "type": "string"
+            },
+            "label": {
+              "description": "Reference label",
+              "type": "string"
+            }
+          },
+          "required": [
+            "citation"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "sections": {
+        "description": "Article body sections",
+        "items": {
+          "additionalProperties": false,
+          "description": "Article body section",
+          "properties": {
+            "label": {
+              "description": "Section label",
+              "type": "string"
+            },
+            "subsections": {
+              "description": "Nested subsections",
+              "items": {
+                "additionalProperties": false,
+                "description": "Article subsection",
+                "properties": {
+                  "label": {
+                    "description": "Subsection label",
+                    "type": "string"
+                  },
+                  "text": {
+                    "description": "Subsection body text. Sections nested deeper than this level are folded in here in document order, each heading rendered on its own line above its text.",
+                    "type": "string"
+                  },
+                  "title": {
+                    "description": "Subsection heading",
+                    "type": "string"
+                  }
+                },
+                "required": [
+                  "text"
+                ],
+                "type": "object"
+              },
+              "type": "array"
+            },
+            "text": {
+              "description": "Section body text",
+              "type": "string"
+            },
+            "title": {
+              "description": "Section heading",
+              "type": "string"
+            }
+          },
+          "required": [
+            "text"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "source": {
+        "const": "pmc",
+        "description": "Structured JATS — same DTD whether sourced from NCBI PMC or Europe PMC",
+        "type": "string"
+      },
+      "title": {
+        "description": "Article title",
+        "type": "string"
+      },
+      "viaSource": {
+        "description": "Which layer produced the JATS: `pmc` for NCBI PMC EFetch (db=pmc), `europepmc` for Europe PMC `fullTextXML`. Both paths return the same JATS shape; the discriminator records origin for observability and license attribution.",
+        "enum": [
+          "pmc",
+          "europepmc"
+        ],
+        "type": "string"
+      }
+    },
+    "required": [
+      "source",
+      "viaSource",
+      "sections"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "description": "Best-effort full text from an open-access copy",
+    "properties": {
+      "content": {
+        "description": "Full article text — Markdown or plain text per `contentFormat`",
+        "type": "string"
+      },
+      "contentFormat": {
+        "description": "How `content` was extracted. html-markdown: Defuddle extracted Markdown from an HTML landing page; light section structure may survive but is not guaranteed. pdf-text: unpdf extracted plain text from a PDF; no section, reference, or heading structure.",
+        "enum": [
+          "html-markdown",
+          "pdf-text"
+        ],
+        "type": "string"
+      },
+      "doi": {
+        "description": "DOI used to locate the open-access copy",
+        "type": "string"
+      },
+      "hostType": {
+        "description": "`publisher` or `repository` — where the OA copy is hosted",
+        "type": "string"
+      },
+      "license": {
+        "description": "License identifier from Unpaywall (e.g. cc-by, cc0)",
+        "type": "string"
+      },
+      "pmcId": {
+        "description": "PMC ID this article was requested under, in `PMC<digits>` form — present for `pmcids` input, absent for `pmids` and `dois` input. Ties the article back to the requested identifier, which `unavailable[]` keys on for the ids that found nothing.",
+        "type": "string"
+      },
+      "pmid": {
+        "description": "PubMed ID when input was `pmids`; absent for `pmcids` and `dois` input",
+        "type": "string"
+      },
+      "pubmedUrl": {
+        "description": "PubMed URL — present when `pmid` is set",
+        "type": "string"
+      },
+      "source": {
+        "const": "unpaywall",
+        "description": "Content fetched from an open-access copy indexed by Unpaywall. Best-effort — structural fidelity depends on `contentFormat`.",
+        "type": "string"
+      },
+      "sourceUrl": {
+        "description": "URL the content was fetched from",
+        "type": "string"
+      },
+      "title": {
+        "description": "Detected article title when present",
+        "type": "string"
+      },
+      "totalPages": {
+        "description": "Page count reported by the PDF extractor; absent for HTML",
+        "type": "number"
+      },
+      "version": {
+        "description": "OA version: submittedVersion | acceptedVersion | publishedVersion",
+        "type": "string"
+      },
+      "viaSource": {
+        "const": "unpaywall",
+        "description": "Layer that produced this article. Constant `unpaywall` for this branch.",
+        "type": "string"
+      },
+      "wordCount": {
+        "description": "Approximate word count reported by the HTML extractor; absent for PDFs",
+        "type": "number"
+      }
+    },
+    "required": [
+      "source",
+      "viaSource",
+      "contentFormat",
+      "doi",
+      "sourceUrl",
+      "content"
+    ],
+    "type": "object"
+  }
+]

Added value: +{
+  "additionalProperties": false,
+  "description": "Continuation state for articles the whole-response budget withheld. Present only when `maxResponseCharacters` deferred at least one article.",
+  "properties": {
+    "deferredCount": {
+      "description": "Articles the chain resolved but withheld to stay under the ceiling",
+      "type": "number"
+    },
+    "idType": {
+      "description": "Which input branch the deferred ids belong to — re-submit them as `pmids`, `pmcids`, or `dois` respectively. Matches the `idType` on `unavailable` entries.",
+      "enum": [
+        "pmid",
+        "pmcid",
+        "doi"
+      ],
+      "type": "string"
+    },
+    "ids": {
+      "description": "Identifiers of the deferred articles, in response order, keyed as they were requested (PMC IDs in `PMC<digits>` form). Re-call `pubmed_fetch_fulltext` with these under the `idType` branch and the same other inputs. Never contains an id from `unavailable`.",
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "maxResponseCharacters": {
+      "description": "The `maxResponseCharacters` ceiling this response was budgeted against",
+      "type": "number"
+    },
+    "nextDeferredCharacters": {
+      "description": "Serialized size of the next deferred article — the first entry in `ids`, where the response stopped. Raise `maxResponseCharacters` to at least this to make progress; a smaller article further down `ids` cannot be reached until this one fits.",
+      "type": "number"
+    },
+    "returnedCharacters": {
+      "description": "Serialized characters the returned article records account for",
+      "type": "number"
+    }
+  },
+  "required": [
+    "maxResponseCharacters",
+    "returnedCharacters",
+    "deferredCount",
+    "idType",
+    "ids",
+    "nextDeferredCharacters"
+  ],
+  "type": "object"
+}

Previous value: -"Optional guidance for a partial or empty body. A `sections`-filter miss names the requested terms and affected article id(s) and suggests retrying without `sections` or using broader headings. A metadata-only record names the id(s) the chain could retrieve as front matter only and points at `pubmed_fetch_articles` for the abstract. A budgeted response names the characters returned versus carried and points at `truncation`. Absent when none of those applies."New value: +"Optional guidance for a partial or empty body. A `sections`-filter miss names the requested terms and affected article id(s) and suggests retrying without `sections` or using broader headings. A metadata-only record names the id(s) the chain could retrieve as front matter only and points at `pubmed_fetch_articles` for the abstract. A budgeted response names the characters returned versus carried and points at `truncation`. A response-wide budget that deferred articles names the ids to re-request. Absent when none of those applies."

Previous value: -"Number of articles returned"New value: +"Number of articles in this response. Under a `maxResponseCharacters` budget this counts the kept articles only; `deferred.deferredCount` covers the rest."

Previous value: -"True when a character budget shortened at least one returned body. Absent when every returned article carries its full post-filter body. The per-article accounting is in `truncation`."New value: +"True when a character budget shortened at least one returned body, or withheld a whole article. Absent when every resolved article is present with its full post-filter body. The per-article body accounting is in `truncation`; the withheld ids are in `deferred`."

Previous value: -"Per-identifier explanations for any requested PMIDs, PMCIDs, or DOIs with no returnable full text. `idType` discriminates which branch the id came from."New value: +"Per-identifier explanations for any requested PMIDs, PMCIDs, or DOIs with no returnable full text. `idType` discriminates which branch the id came from. Distinct from `deferred`: nothing here is retrievable by re-calling, and an id never appears in both."

Previous value: -"Why no full text was returned. not-found: upstream returned no record for this ID. no-pmc-fallback-disabled: every tier was skipped (`triedTiers` is all `not-attempted`) — typically because EPMC (`EUROPEPMC_ENABLED`) and Unpaywall (`UNPAYWALL_EMAIL`) are not configured. no-epmc-fulltext: EPMC indexed the record but publishes no fullTextXML. no-body: the record was retrieved but carries front matter and abstract only, with no body sections — use `pubmed_fetch_articles` for the metadata. no-doi: no DOI to query Unpaywall. no-oa: Unpaywall has no OA copy. fetch-failed: download failed. parse-failed: extraction empty. service-error: upstream server failure (threw, timed out, or returned malformed data)."New value: +"Why no full text was returned — the most specific signal any tier that answered reported. not-found: upstream returned no record for this ID. no-pmc-fallback-disabled: every tier was skipped (`triedTiers` is all `not-attempted`) — typically because EPMC (`EUROPEPMC_ENABLED`) and Unpaywall (`UNPAYWALL_EMAIL`) are not configured. no-epmc-fulltext: EPMC indexed the record but publishes no fullTextXML. no-body: the record was retrieved but carries front matter and abstract only, with no body sections — use `pubmed_fetch_articles` for the metadata. no-doi: no DOI to query Unpaywall. no-oa: Unpaywall has no OA copy. fetch-failed: download failed. parse-failed: extraction empty. service-error: upstream server failure (threw, timed out, or returned malformed data). A reason never means the chain ran to completion — read `unqueriedTiers` for that."

Added value: +{
+  "description": "Tiers the chain skipped because this deployment has not configured them, and that could have served this id — the search was incomplete, and a deployment with these tiers configured may still resolve the id. `triedTiers` carries which environment variable each one is waiting on. Absent when every tier that could have served the id was actually queried; a tier skipped because it was inapplicable to this id (no DOI for Unpaywall) is never listed.",
+  "items": {
+    "description": "A fallback tier this deployment has not configured",
+    "enum": [
+      "europepmc",
+      "unpaywall"
+    ],
+    "type": "string"
+  },
+  "type": "array"
+}

Previous value: -"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `europepmc_unreachable`: Europe PMC was unreachable after all retry attempts. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input (empty query, unknown sort field, malformed parameter). `openalex_unreachable`: OpenAlex was unreachable after all retry attempts. `openalex_invalid_response`: OpenAlex returned a body that could not be parsed (invalid JSON). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `europepmc_unreachable`: Europe PMC was unreachable after all retry attempts. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input (empty query, unknown sort field, malformed parameter). `openalex_unreachable`: OpenAlex was unreachable after all retry attempts. `openalex_invalid_response`: OpenAlex returned a body that could not be parsed (invalid JSON). `all_providers_failed`: Every provider eligible for the requested relationship failed; none answered. Other values are possible when a failure originates below the handler."

Previous value: -[
-  "queue_full",
-  "ncbi_unreachable",
-  "ncbi_deadline_exceeded",
-  "ncbi_invalid_response",
-  "ncbi_resource_not_found",
-  "europepmc_unreachable",
-  "europepmc_invalid_response",
-  "europepmc_invalid_input",
-  "openalex_unreachable",
-  "openalex_invalid_response"
-]New value: +[
+  "queue_full",
+  "ncbi_unreachable",
+  "ncbi_deadline_exceeded",
+  "ncbi_invalid_response",
+  "ncbi_resource_not_found",
+  "europepmc_unreachable",
+  "europepmc_invalid_response",
+  "europepmc_invalid_input",
+  "openalex_unreachable",
+  "openalex_invalid_response",
+  "all_providers_failed"
+]

Previous value: -"Guidance when results are empty, a fallback provider answered, or offset overshot. Absent on a clean NCBI result page."New value: +"Guidance when results are empty, a fallback provider answered, offset overshot, or Europe PMC rows were excluded for carrying no PubMed PMID. Absent on a clean NCBI result page."

Previous value: -"Total related articles found before windowing"New value: +"Total related articles found before windowing. A Europe PMC total may shrink to the PubMed-addressable count once a request window covers the whole upstream set, since rows without a PubMed PMID cannot be returned."

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "records",
+      "totalConverted",
+      "totalSubmitted"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "queue_full",
+            "ncbi_unreachable",
+            "ncbi_deadline_exceeded",
+            "ncbi_invalid_response",
+            "ncbi_resource_not_found"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Removed value: -[
-  "records",
-  "totalConverted",
-  "totalSubmitted"
-]

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "records"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `europepmc_unreachable`: Europe PMC was unreachable after all retry attempts. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input (empty query, unknown sort field, malformed parameter). `europepmc_disabled`: Europe PMC service is disabled via EUROPEPMC_ENABLED=false. Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "europepmc_unreachable",
+            "europepmc_invalid_response",
+            "europepmc_invalid_input",
+            "europepmc_disabled"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Removed value: -[
-  "records"
-]

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "hits",
+      "cursorMark",
+      "searchUrl",
+      "query",
+      "totalCount",
+      "appliedSources"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `europepmc_unreachable`: Europe PMC was unreachable after all retry attempts. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input (empty query, unknown sort field, malformed parameter). `europepmc_disabled`: Europe PMC service is disabled via EUROPEPMC_ENABLED=false. Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "europepmc_unreachable",
+            "europepmc_invalid_response",
+            "europepmc_invalid_input",
+            "europepmc_disabled"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Removed value: -[
-  "hits",
-  "cursorMark",
-  "searchUrl",
-  "query",
-  "totalCount",
-  "appliedSources"
-]

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "articles",
+      "totalReturned"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `invalid_efetch_response`: NCBI EFetch returned a payload missing the PubmedArticleSet wrapper. Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "queue_full",
+            "ncbi_unreachable",
+            "ncbi_deadline_exceeded",
+            "ncbi_invalid_response",
+            "ncbi_resource_not_found",
+            "invalid_efetch_response"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Removed value: -[
-  "articles",
-  "totalReturned"
-]

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "articles",
+      "totalReturned"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `unpaywall_unreachable`: Unpaywall was unreachable when resolving a DOI or fetching content. `europepmc_unreachable`: Europe PMC was unreachable after all retry attempts. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input (empty query, unknown sort field, malformed parameter). Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "queue_full",
+            "ncbi_unreachable",
+            "ncbi_deadline_exceeded",
+            "ncbi_invalid_response",
+            "ncbi_resource_not_found",
+            "unpaywall_unreachable",
+            "europepmc_unreachable",
+            "europepmc_invalid_response",
+            "europepmc_invalid_input"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Added value: +{
+  "description": "True when a character budget shortened at least one returned body. Absent when every returned article carries its full post-filter body. The per-article accounting is in `truncation`.",
+  "type": "boolean"
+}

Removed value: -[
-  "articles",
-  "totalReturned"
-]

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "sourcePmid",
+      "relationship",
+      "offset",
+      "articles",
+      "totalCount",
+      "source"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). `europepmc_unreachable`: Europe PMC was unreachable after all retry attempts. `europepmc_invalid_response`: Europe PMC returned a body that could not be parsed (invalid JSON or XML). `europepmc_invalid_input`: Europe PMC rejected the request input (empty query, unknown sort field, malformed parameter). `openalex_unreachable`: OpenAlex was unreachable after all retry attempts. `openalex_invalid_response`: OpenAlex returned a body that could not be parsed (invalid JSON). Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "queue_full",
+            "ncbi_unreachable",
+            "ncbi_deadline_exceeded",
+            "ncbi_invalid_response",
+            "ncbi_resource_not_found",
+            "europepmc_unreachable",
+            "europepmc_invalid_response",
+            "europepmc_invalid_input",
+            "openalex_unreachable",
+            "openalex_invalid_response"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Removed value: -[
-  "sourcePmid",
-  "relationship",
-  "offset",
-  "articles",
-  "totalCount",
-  "source"
-]

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "citations",
+      "totalSubmitted",
+      "totalFormatted"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "queue_full",
+            "ncbi_unreachable",
+            "ncbi_deadline_exceeded",
+            "ncbi_invalid_response",
+            "ncbi_resource_not_found"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Removed value: -[
-  "citations",
-  "totalSubmitted",
-  "totalFormatted"
-]

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "results",
+      "totalMatched",
+      "totalSubmitted",
+      "totalWarnings"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "queue_full",
+            "ncbi_unreachable",
+            "ncbi_deadline_exceeded",
+            "ncbi_invalid_response",
+            "ncbi_resource_not_found"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Removed value: -[
-  "results",
-  "totalMatched",
-  "totalSubmitted",
-  "totalWarnings"
-]

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "query",
+      "offset",
+      "results",
+      "totalCount"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "queue_full",
+            "ncbi_unreachable",
+            "ncbi_deadline_exceeded",
+            "ncbi_invalid_response",
+            "ncbi_resource_not_found"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Removed value: -[
-  "query",
-  "offset",
-  "results",
-  "totalCount"
-]

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "query",
+      "offset",
+      "pmids",
+      "summaries",
+      "searchUrl",
+      "effectiveQuery",
+      "totalCount",
+      "appliedFilters"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "queue_full",
+            "ncbi_unreachable",
+            "ncbi_deadline_exceeded",
+            "ncbi_invalid_response",
+            "ncbi_resource_not_found"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Removed value: -[
-  "query",
-  "offset",
-  "pmids",
-  "summaries",
-  "searchUrl",
-  "effectiveQuery",
-  "totalCount",
-  "appliedFilters"
-]

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +false

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "original",
+      "corrected",
+      "hasSuggestion"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `queue_full`: Local NCBI request queue is at capacity. `ncbi_unreachable`: NCBI E-utilities is unreachable after all retry attempts. `ncbi_deadline_exceeded`: Total request deadline expired before NCBI returned a response. `ncbi_invalid_response`: NCBI returned a body that could not be parsed (invalid XML/JSON). `ncbi_resource_not_found`: NCBI returned a structured \"not found\" error for the requested ID(s). Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "queue_full",
+            "ncbi_unreachable",
+            "ncbi_deadline_exceeded",
+            "ncbi_invalid_response",
+            "ncbi_resource_not_found"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

Removed value: -[
-  "original",
-  "corrected",
-  "hasSuggestion"
-]

Previous value: -"Digital Object Identifier; absent if no DOI is on record"New value: +"Digital Object Identifier, cased as the PMC ID Converter reports it; absent if no DOI is on record. DOIs are case-insensitive by spec and no case normalization is applied here, so casing can differ from a Europe PMC-sourced `doi` — compare the two case-insensitively."

Previous value: -"Europe PMC search query. Supports field tokens like `AUTH:\"<name>\"`, `JOURNAL:\"<title>\"`, `TITLE:\"<words>\"`, `PUB_YEAR:[2020 TO 2024]`, `DOI:\"...\"`, `EXT_ID:\"<pmid>\" AND SRC:MED`. Free text is matched broadly across abstract/title/keywords."New value: +"Europe PMC search query. Supports field tokens like `AUTH:\"<name>\"`, `JOURNAL:\"<title>\"`, `TITLE:\"<words>\"`, `PUB_YEAR:[2020 TO 2024]`, `DOI:\"...\"`, `EXT_ID:<pmid> AND SRC:MED`, `PMCID:PMC<digits>`. Identifier tokens combined with `AND SRC:` must be unquoted — the quoted form matches nothing. Free text is matched broadly across abstract/title/keywords."

Previous value: -"First few hundred characters of the abstract as display-ready plain text — JATS/HTML markup stripped and HTML entities decoded — when `resultType: \"core\"` is requested"New value: +"First 400 characters of the abstract as display-ready plain text — JATS/HTML markup stripped and HTML entities decoded — when `resultType: \"core\"` is requested, with a trailing … appended when the abstract was cut. Check `abstractTruncated` before treating it as the whole abstract."

Added value: +{
+  "description": "Whether `abstractSnippet` was cut short of the full abstract. Retrieve the complete text with `pubmed_europepmc_fetch` using this record’s `source` and `epmcId`. Present whenever `abstractSnippet` is; omitted when Europe PMC carries no abstract.",
+  "type": "boolean"
+}

Previous value: -"DOI when present"New value: +"DOI when present, cased as Europe PMC reports it. DOIs are case-insensitive by spec and no case normalization is applied here, so the same DOI can arrive in a different case from `pubmed_fetch_articles` (Europe PMC `10.1056/nejmoa2212948`, NCBI `10.1056/NEJMoa2212948`) — a byte-for-byte comparison across the two reports a false mismatch."

Previous value: -"Europe PMC's internal record id; key for `fullTextXML` lookup"New value: +"Europe PMC's internal record id. Pass it with this hit's `source` to `pubmed_europepmc_fetch` for the complete record. Europe PMC's `fullTextXML` is keyed on `pmcId`, not on this id, so records without a PMC counterpart have no full text to fetch."

Previous value: -"DOI"New value: +"DOI, cased as NCBI reports it (usually the publisher's mixed case). DOIs are case-insensitive by spec and no case normalization is applied here, so the same DOI can arrive in a different case from `pubmed_europepmc_search` and `pubmed_europepmc_fetch` (NCBI `10.1056/NEJMoa2212948`, Europe PMC `10.1056/nejmoa2212948`) — a byte-for-byte comparison across the two reports a false mismatch."

Added value: +{
+  "description": "Per-article budget for body text, in characters. Counts `source=pmc` section and subsection text, or the `source=unpaywall` `content` body; titles, abstracts, identifiers, and references are never counted or shortened. Applied after `sections`, `maxSections`, and `includeReferences`, so semantic filtering is unaffected. The response-wide ceiling is this value times the number of articles returned. Omit for the full body.",
+  "maximum": 1000000,
+  "minimum": 1,
+  "type": "integer"
+}

Added value: +{
+  "description": "Budget for a single top-level body section, in characters, counting the section text plus its subsections. Combine with `maxCharacters` to cap both one section and the article; the tighter of the two wins. Applies to `source=pmc` results only.",
+  "maximum": 1000000,
+  "minimum": 1,
+  "type": "integer"
+}

Added value: +{
+  "default": "truncate",
+  "description": "How to spend `maxCharacters` across an article that exceeds it. truncate: fill sections in document order, so early sections stay whole and sections past the budget are dropped (counted in `truncation.omittedSections`). outline: split the budget evenly so every section keeps its heading, and an excerpt as far as the budget reaches — use it to survey what an article contains before requesting specific `sections`. Ignored when no budget is set, and identical for `source=unpaywall` bodies, which have no headings to preserve.",
+  "enum": [
+    "truncate",
+    "outline"
+  ],
+  "type": "string"
+}

Previous value: -"PMC IDs to fetch (e.g. [\"PMC9575052\"]). Provide exactly one of `pmcids`, `pmids`, or `dois`."New value: +"PMC IDs to fetch (e.g. [\"PMC9575052\"]). Provide exactly one of `pmcids`, `pmids`, or `dois`. PMC IDs with no retrievable full text fall through to Europe PMC, then to Unpaywall on the DOI the chain resolves for them."

Previous value: -[
-  {
-    "additionalProperties": false,
-    "description": "Structured JATS full-text article. `viaSource` records whether the JATS came from NCBI PMC or Europe PMC.",
-    "properties": {
-      "abstract": {
-        "description": "Abstract",
-        "type": "string"
-      },
-      "affiliations": {
-        "description": "Author affiliations",
-        "items": {
-          "type": "string"
-        },
-        "type": "array"
-      },
-      "articleType": {
-        "description": "Article type",
-        "type": "string"
-      },
-      "authors": {
-        "description": "Authors",
-        "items": {
-          "additionalProperties": false,
-          "description": "Author entry",
-          "properties": {
-            "collectiveName": {
-              "description": "Group name",
-              "type": "string"
-            },
-            "givenNames": {
-              "description": "Given names",
-              "type": "string"
-            },
-            "lastName": {
-              "description": "Last name",
-              "type": "string"
-            }
-          },
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "doi": {
-        "description": "DOI",
-        "type": "string"
-      },
-      "epmcId": {
-        "description": "Europe PMC record id — present when `viaSource` is `europepmc`",
-        "type": "string"
-      },
-      "epmcSource": {
-        "description": "Europe PMC source code when `viaSource` is `europepmc`. Common values: `MED` (PubMed-derived), `PMC` (PMC counterpart), `PPR` (preprint), `PAT` (patent), `AGR` (Agricola), plus less common codes (`CTX`, `CBA`, `ETH`, `HIR`). Treat as opaque — EPMC may introduce new codes.",
-        "type": "string"
-      },
-      "journal": {
-        "additionalProperties": false,
-        "description": "Journal information",
-        "properties": {
-          "issn": {
-            "description": "ISSN",
-            "type": "string"
-          },
-          "issue": {
-            "description": "Issue number",
-            "type": "string"
-          },
-          "pages": {
-            "description": "Page range",
-            "type": "string"
-          },
-          "title": {
-            "description": "Journal title",
-            "type": "string"
-          },
-          "volume": {
-            "description": "Volume number",
-            "type": "string"
-          }
-        },
-        "type": "object"
-      },
-      "keywords": {
-        "description": "Keywords",
-        "items": {
-          "type": "string"
-        },
-        "type": "array"
-      },
-      "pmcId": {
-        "description": "PMC ID — present for NCBI PMC records and Europe PMC entries that have a PMC counterpart. Absent for EPMC-only records like preprints; use `epmcId` in that case.",
-        "type": "string"
-      },
-      "pmcUrl": {
-        "description": "PMC URL — derived from `pmcId` when present",
-        "type": "string"
-      },
-      "pmid": {
-        "description": "PubMed ID",
-        "type": "string"
-      },
-      "publicationDate": {
-        "additionalProperties": false,
-        "description": "Publication date",
-        "properties": {
-          "day": {
-            "description": "Publication day",
-            "type": "string"
-          },
-          "month": {
-            "description": "Publication month",
-            "type": "string"
-          },
-          "year": {
-            "description": "Publication year",
-            "type": "string"
-          }
-        },
-        "type": "object"
-      },
-      "pubmedUrl": {
-        "description": "PubMed URL",
-        "type": "string"
-      },
-      "references": {
-        "description": "Reference list",
-        "items": {
-          "additionalProperties": false,
-          "description": "Reference entry",
-          "properties": {
-            "citation": {
-              "description": "Citation text",
-              "type": "string"
-            },
-            "id": {
-              "description": "Reference ID",
-              "type": "string"
-            },
-            "label": {
-              "description": "Reference label",
-              "type": "string"
-            }
-          },
-          "required": [
-            "citation"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "sections": {
-        "description": "Article body sections",
-        "items": {
-          "additionalProperties": false,
-          "description": "Article body section",
-          "properties": {
-            "label": {
-              "description": "Section label",
-              "type": "string"
-            },
-            "subsections": {
-              "description": "Nested subsections",
-              "items": {
-                "additionalProperties": false,
-                "description": "Article subsection",
-                "properties": {
-                  "label": {
-                    "description": "Subsection label",
-                    "type": "string"
-                  },
-                  "text": {
-                    "description": "Subsection body text",
-                    "type": "string"
-                  },
-                  "title": {
-                    "description": "Subsection heading",
-                    "type": "string"
-                  }
-                },
-                "required": [
-                  "text"
-                ],
-                "type": "object"
-              },
-              "type": "array"
-            },
-            "text": {
-              "description": "Section body text",
-              "type": "string"
-            },
-            "title": {
-              "description": "Section heading",
-              "type": "string"
-            }
-          },
-          "required": [
-            "text"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "source": {
-        "const": "pmc",
-        "description": "Structured JATS — same DTD whether sourced from NCBI PMC or Europe PMC",
-        "type": "string"
-      },
-      "title": {
-        "description": "Article title",
-        "type": "string"
-      },
-      "viaSource": {
-        "description": "Which layer produced the JATS: `pmc` for NCBI PMC EFetch (db=pmc), `europepmc` for Europe PMC `fullTextXML`. Both paths return the same JATS shape; the discriminator records origin for observability and license attribution.",
-        "enum": [
-          "pmc",
-          "europepmc"
-        ],
-        "type": "string"
-      }
-    },
-    "required": [
-      "source",
-      "viaSource",
-      "sections"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "description": "Best-effort full text from an open-access copy",
-    "properties": {
-      "content": {
-        "description": "Full article text — Markdown or plain text per `contentFormat`",
-        "type": "string"
-      },
-      "contentFormat": {
-        "description": "How `content` was extracted. html-markdown: Defuddle extracted Markdown from an HTML landing page; light section structure may survive but is not guaranteed. pdf-text: unpdf extracted plain text from a PDF; no section, reference, or heading structure.",
-        "enum": [
-          "html-markdown",
-          "pdf-text"
-        ],
-        "type": "string"
-      },
-      "doi": {
-        "description": "DOI used to locate the open-access copy",
-        "type": "string"
-      },
-      "hostType": {
-        "description": "`publisher` or `repository` — where the OA copy is hosted",
-        "type": "string"
-      },
-      "license": {
-        "description": "License identifier from Unpaywall (e.g. cc-by, cc0)",
-        "type": "string"
-      },
-      "pmid": {
-        "description": "PubMed ID when input was `pmids`; absent for `dois` input",
-        "type": "string"
-      },
-      "pubmedUrl": {
-        "description": "PubMed URL — present when `pmid` is set",
-        "type": "string"
-      },
-      "source": {
-        "const": "unpaywall",
-        "description": "Content fetched from an open-access copy indexed by Unpaywall. Best-effort — structural fidelity depends on `contentFormat`.",
-        "type": "string"
-      },
-      "sourceUrl": {
-        "description": "URL the content was fetched from",
-        "type": "string"
-      },
-      "title": {
-        "description": "Detected article title when present",
-        "type": "string"
-      },
-      "totalPages": {
-        "description": "Page count reported by the PDF extractor; absent for HTML",
-        "type": "number"
-      },
-      "version": {
-        "description": "OA version: submittedVersion | acceptedVersion | publishedVersion",
-        "type": "string"
-      },
-      "viaSource": {
-        "const": "unpaywall",
-        "description": "Layer that produced this article. Constant `unpaywall` for this branch.",
-        "type": "string"
-      },
-      "wordCount": {
-        "description": "Approximate word count reported by the HTML extractor; absent for PDFs",
-        "type": "number"
-      }
-    },
-    "required": [
-      "source",
-      "viaSource",
-      "contentFormat",
-      "doi",
-      "sourceUrl",
-      "content"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "description": "Structured JATS full-text article. `viaSource` records whether the JATS came from NCBI PMC or Europe PMC.",
+    "properties": {
+      "abstract": {
+        "description": "Abstract",
+        "type": "string"
+      },
+      "affiliations": {
+        "description": "Author affiliations",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "articleType": {
+        "description": "Article type",
+        "type": "string"
+      },
+      "authors": {
+        "description": "Authors",
+        "items": {
+          "additionalProperties": false,
+          "description": "Author entry",
+          "properties": {
+            "collectiveName": {
+              "description": "Group name",
+              "type": "string"
+            },
+            "givenNames": {
+              "description": "Given names",
+              "type": "string"
+            },
+            "lastName": {
+              "description": "Last name",
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "doi": {
+        "description": "DOI, cased as the tier that served this record reports it (NCBI PMC, Europe PMC, or Unpaywall). DOIs are case-insensitive by spec and no case normalization is applied here, so casing can differ between tiers and from other tools — compare case-insensitively.",
+        "type": "string"
+      },
+      "epmcId": {
+        "description": "Europe PMC record id — present when `viaSource` is `europepmc`",
+        "type": "string"
+      },
+      "epmcSource": {
+        "description": "Europe PMC source code when `viaSource` is `europepmc`. Common values: `MED` (PubMed-derived), `PMC` (PMC counterpart), `PPR` (preprint), `PAT` (patent), `AGR` (Agricola), plus less common codes (`CTX`, `CBA`, `ETH`, `HIR`). Treat as opaque — EPMC may introduce new codes.",
+        "type": "string"
+      },
+      "journal": {
+        "additionalProperties": false,
+        "description": "Journal information",
+        "properties": {
+          "issn": {
+            "description": "ISSN",
+            "type": "string"
+          },
+          "issue": {
+            "description": "Issue number",
+            "type": "string"
+          },
+          "pages": {
+            "description": "Page range",
+            "type": "string"
+          },
+          "title": {
+            "description": "Journal title",
+            "type": "string"
+          },
+          "volume": {
+            "description": "Volume number",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "keywords": {
+        "description": "Keywords",
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "pmcId": {
+        "description": "PMC ID — present for NCBI PMC records and Europe PMC entries that have a PMC counterpart. Absent for EPMC-only records like preprints; use `epmcId` in that case.",
+        "type": "string"
+      },
+      "pmcUrl": {
+        "description": "PMC URL — derived from `pmcId` when present",
+        "type": "string"
+      },
+      "pmid": {
+        "description": "PubMed ID",
+        "type": "string"
+      },
+      "publicationDate": {
+        "additionalProperties": false,
+        "description": "Publication date",
+        "properties": {
+          "day": {
+            "description": "Publication day",
+            "type": "string"
+          },
+          "month": {
+            "description": "Publication month",
+            "type": "string"
+          },
+          "year": {
+            "description": "Publication year",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "pubmedUrl": {
+        "description": "PubMed URL",
+        "type": "string"
+      },
+      "references": {
+        "description": "Reference list",
+        "items": {
+          "additionalProperties": false,
+          "description": "Reference entry",
+          "properties": {
+            "citation": {
+              "description": "Citation text",
+              "type": "string"
+            },
+            "id": {
+              "description": "Reference ID",
+              "type": "string"
+            },
+            "label": {
+              "description": "Reference label",
+              "type": "string"
+            }
+          },
+          "required": [
+            "citation"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "sections": {
+        "description": "Article body sections",
+        "items": {
+          "additionalProperties": false,
+          "description": "Article body section",
+          "properties": {
+            "label": {
+              "description": "Section label",
+              "type": "string"
+            },
+            "subsections": {
+              "description": "Nested subsections",
+              "items": {
+                "additionalProperties": false,
+                "description": "Article subsection",
+                "properties": {
+                  "label": {
+                    "description": "Subsection label",
+                    "type": "string"
+                  },
+                  "text": {
+                    "description": "Subsection body text",
+                    "type": "string"
+                  },
+                  "title": {
+                    "description": "Subsection heading",
+                    "type": "string"
+                  }
+                },
+                "required": [
+                  "text"
+                ],
+                "type": "object"
+              },
+              "type": "array"
+            },
+            "text": {
+              "description": "Section body text",
+              "type": "string"
+            },
+            "title": {
+              "description": "Section heading",
+              "type": "string"
+            }
+          },
+          "required": [
+            "text"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "source": {
+        "const": "pmc",
+        "description": "Structured JATS — same DTD whether sourced from NCBI PMC or Europe PMC",
+        "type": "string"
+      },
+      "title": {
+        "description": "Article title",
+        "type": "string"
+      },
+      "viaSource": {
+        "description": "Which layer produced the JATS: `pmc` for NCBI PMC EFetch (db=pmc), `europepmc` for Europe PMC `fullTextXML`. Both paths return the same JATS shape; the discriminator records origin for observability and license attribution.",
+        "enum": [
+          "pmc",
+          "europepmc"
+        ],
+        "type": "string"
+      }
+    },
+    "required": [
+      "source",
+      "viaSource",
+      "sections"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "description": "Best-effort full text from an open-access copy",
+    "properties": {
+      "content": {
+        "description": "Full article text — Markdown or plain text per `contentFormat`",
+        "type": "string"
+      },
+      "contentFormat": {
+        "description": "How `content` was extracted. html-markdown: Defuddle extracted Markdown from an HTML landing page; light section structure may survive but is not guaranteed. pdf-text: unpdf extracted plain text from a PDF; no section, reference, or heading structure.",
+        "enum": [
+          "html-markdown",
+          "pdf-text"
+        ],
+        "type": "string"
+      },
+      "doi": {
+        "description": "DOI used to locate the open-access copy",
+        "type": "string"
+      },
+      "hostType": {
+        "description": "`publisher` or `repository` — where the OA copy is hosted",
+        "type": "string"
+      },
+      "license": {
+        "description": "License identifier from Unpaywall (e.g. cc-by, cc0)",
+        "type": "string"
+      },
+      "pmcId": {
+        "description": "PMC ID this article was requested under, in `PMC<digits>` form — present for `pmcids` input, absent for `pmids` and `dois` input. Ties the article back to the requested identifier, which `unavailable[]` keys on for the ids that found nothing.",
+        "type": "string"
+      },
+      "pmid": {
+        "description": "PubMed ID when input was `pmids`; absent for `pmcids` and `dois` input",
+        "type": "string"
+      },
+      "pubmedUrl": {
+        "description": "PubMed URL — present when `pmid` is set",
+        "type": "string"
+      },
+      "source": {
+        "const": "unpaywall",
+        "description": "Content fetched from an open-access copy indexed by Unpaywall. Best-effort — structural fidelity depends on `contentFormat`.",
+        "type": "string"
+      },
+      "sourceUrl": {
+        "description": "URL the content was fetched from",
+        "type": "string"
+      },
+      "title": {
+        "description": "Detected article title when present",
+        "type": "string"
+      },
+      "totalPages": {
+        "description": "Page count reported by the PDF extractor; absent for HTML",
+        "type": "number"
+      },
+      "version": {
+        "description": "OA version: submittedVersion | acceptedVersion | publishedVersion",
+        "type": "string"
+      },
+      "viaSource": {
+        "const": "unpaywall",
+        "description": "Layer that produced this article. Constant `unpaywall` for this branch.",
+        "type": "string"
+      },
+      "wordCount": {
+        "description": "Approximate word count reported by the HTML extractor; absent for PDFs",
+        "type": "number"
+      }
+    },
+    "required": [
+      "source",
+      "viaSource",
+      "contentFormat",
+      "doi",
+      "sourceUrl",
+      "content"
+    ],
+    "type": "object"
+  }
+]

Previous value: -"Optional guidance when a `sections` filter removed every body section — names the requested section terms and the affected article id(s), and suggests retrying without `sections` or using broader headings. Absent when no section filter was applied or sections matched."New value: +"Optional guidance for a partial or empty body. A `sections`-filter miss names the requested terms and affected article id(s) and suggests retrying without `sections` or using broader headings. A metadata-only record names the id(s) the chain could retrieve as front matter only and points at `pubmed_fetch_articles` for the abstract. A budgeted response names the characters returned versus carried and points at `truncation`. Absent when none of those applies."

Added value: +{
+  "additionalProperties": false,
+  "description": "Character accounting for full text the budget shortened. Present only when a budget actually removed characters — its absence means every returned article carries its full post-filter body.",
+  "properties": {
+    "articles": {
+      "description": "Per-article accounting, covering only the articles the budget shortened",
+      "items": {
+        "additionalProperties": false,
+        "description": "Character accounting for one article the budget shortened",
+        "properties": {
+          "id": {
+            "description": "Identifier for the article — PMCID, PMID, DOI, or Europe PMC id, whichever the article carries first",
+            "type": "string"
+          },
+          "originalCharacters": {
+            "description": "Body characters this article carried before the budget pass",
+            "type": "number"
+          },
+          "returnedCharacters": {
+            "description": "Body characters this article carries in the response",
+            "type": "number"
+          },
+          "sections": {
+            "description": "Per-section accounting for `source: pmc` articles, in document order, including sections dropped for budget. Absent for `source: unpaywall`, whose body has no section structure.",
+            "items": {
+              "additionalProperties": false,
+              "description": "Character accounting for one body section of a budgeted article",
+              "properties": {
+                "originalCharacters": {
+                  "description": "Body characters this section carried before the budget pass",
+                  "type": "number"
+                },
+                "returnedCharacters": {
+                  "description": "Body characters this section carries in the response. Zero means the section was dropped in `truncate` mode, or kept as a heading-only entry in `outline` mode.",
+                  "type": "number"
+                },
+                "title": {
+                  "description": "Section heading, when the section carries one",
+                  "type": "string"
+                },
+                "truncated": {
+                  "description": "True when the section returned fewer characters than it originally carried",
+                  "type": "boolean"
+                }
+              },
+              "required": [
+                "originalCharacters",
+                "returnedCharacters",
+                "truncated"
+              ],
+              "type": "object"
+            },
+            "type": "array"
+          },
+          "source": {
+            "description": "Which output shape was budgeted: `pmc` budgets body sections and subsections, `unpaywall` budgets the single `content` body",
+            "enum": [
+              "pmc",
+              "unpaywall"
+            ],
+            "type": "string"
+          }
+        },
+        "required": [
+          "id",
+          "source",
+          "originalCharacters",
+          "returnedCharacters"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "maxCharacters": {
+      "description": "The `maxCharacters` budget applied, when set",
+      "type": "number"
+    },
+    "maxCharactersPerSection": {
+      "description": "The `maxCharactersPerSection` budget applied, when set",
+      "type": "number"
+    },
+    "mode": {
+      "description": "The `overflowMode` that produced these results",
+      "enum": [
+        "truncate",
+        "outline"
+      ],
+      "type": "string"
+    },
+    "omittedSections": {
+      "description": "Body sections dropped entirely because an article budget was exhausted before reaching them. Always 0 in `outline` mode, which keeps every heading.",
+      "type": "number"
+    },
+    "originalCharacters": {
+      "description": "Body characters the shortened articles carried before the budget pass",
+      "type": "number"
+    },
+    "returnedCharacters": {
+      "description": "Body characters the shortened articles carry in this response",
+      "type": "number"
+    }
+  },
+  "required": [
+    "mode",
+    "originalCharacters",
+    "returnedCharacters",
+    "omittedSections",
+    "articles"
+  ],
+  "type": "object"
+}

Previous value: -"Why no full text was returned. not-found: upstream returned no record for this ID. no-pmc-fallback-disabled: every tier was skipped (`triedTiers` is all `not-attempted`) — typically because EPMC (`EUROPEPMC_ENABLED`) and Unpaywall (`UNPAYWALL_EMAIL`) are not configured. no-epmc-fulltext: EPMC indexed the record but publishes no fullTextXML. no-doi: no DOI to query Unpaywall. no-oa: Unpaywall has no OA copy. fetch-failed: download failed. parse-failed: extraction empty. service-error: upstream server failure (threw, timed out, or returned malformed data)."New value: +"Why no full text was returned. not-found: upstream returned no record for this ID. no-pmc-fallback-disabled: every tier was skipped (`triedTiers` is all `not-attempted`) — typically because EPMC (`EUROPEPMC_ENABLED`) and Unpaywall (`UNPAYWALL_EMAIL`) are not configured. no-epmc-fulltext: EPMC indexed the record but publishes no fullTextXML. no-body: the record was retrieved but carries front matter and abstract only, with no body sections — use `pubmed_fetch_articles` for the metadata. no-doi: no DOI to query Unpaywall. no-oa: Unpaywall has no OA copy. fetch-failed: download failed. parse-failed: extraction empty. service-error: upstream server failure (threw, timed out, or returned malformed data)."

Previous value: -[
-  "not-found",
-  "no-pmc-fallback-disabled",
-  "no-epmc-fulltext",
-  "no-doi",
-  "no-oa",
-  "fetch-failed",
-  "parse-failed",
-  "service-error"
-]New value: +[
+  "not-found",
+  "no-pmc-fallback-disabled",
+  "no-epmc-fulltext",
+  "no-body",
+  "no-doi",
+  "no-oa",
+  "fetch-failed",
+  "parse-failed",
+  "service-error"
+]

Previous value: -"Per-tier outcome. not-attempted: tier was skipped. miss: tier returned no record. no-fulltext: EPMC indexed the record but publishes no fullTextXML. no-doi: no DOI to query Unpaywall. no-oa: Unpaywall reports no open-access copy. fetch-failed: OA copy download failed. parse-failed: extraction produced empty content. service-error: tier service threw."New value: +"Per-tier outcome. not-attempted: tier was skipped. miss: tier returned no record. no-fulltext: EPMC indexed the record but publishes no fullTextXML. no-body: the tier returned a record with front matter and abstract but no body sections, so the chain continued. no-doi: no DOI to query Unpaywall. no-oa: Unpaywall reports no open-access copy. fetch-failed: OA copy download failed. parse-failed: extraction produced empty content. service-error: tier service threw."

Previous value: -[
-  "not-attempted",
-  "miss",
-  "no-fulltext",
-  "no-doi",
-  "no-oa",
-  "fetch-failed",
-  "parse-failed",
-  "service-error"
-]New value: +[
+  "not-attempted",
+  "miss",
+  "no-fulltext",
+  "no-body",
+  "no-doi",
+  "no-oa",
+  "fetch-failed",
+  "parse-failed",
+  "service-error"
+]

Added value: +{
+  "default": 0,
+  "description": "Result offset for pagination (0-based). Pass the `nextOffset` from the previous response to get the following page; the exact-descriptor match is pinned to the first page only.",
+  "maximum": 9007199254740991,
+  "minimum": 0,
+  "type": "integer"
+}

Added value: +{
+  "description": "Offset to request for the next page. Omitted when this is the last page, so its absence is the end-of-results signal.",
+  "type": "number"
+}

Previous value: -"Optional guidance when no descriptors matched — suggests spell-check or free-text search. Absent on successful results."New value: +"Optional guidance when no descriptors matched or the offset overshot the result set — suggests spell-check, free-text search, or resetting the offset. Absent on successful result pages."

Added value: +{
+  "description": "Result offset this page was read from",
+  "type": "number"
+}

Previous value: -"Total matching MeSH descriptors"New value: +"Total MeSH descriptors matching the query upstream, before the maxResults cap"

Previous value: -[
-  "query",
-  "results",
-  "totalCount"
-]New value: +[
+  "query",
+  "offset",
+  "results",
+  "totalCount"
+]

Previous value: -"Result offset for pagination (0-based)"New value: +"Result offset for pagination (0-based). PubMed serves at most the first 9999 records of a result set, so this caps at 9998; narrow the query or add filters to reach anything beyond it."

Previous value: -9007199254740991New value: +9998

Previous value: -"Fetch brief summaries for top N results (0 = PMIDs only)"New value: +"Fetch brief summaries for top N results (0 = PMIDs only). Above the 50 cap, pass the remaining PMIDs to pubmed_fetch_articles."

Previous value: -"Optional guidance when results are empty or paging overshot — e.g. how to broaden filters or reset offset. Absent on successful result pages."New value: +"Optional guidance when the result set does not reflect what was asked for — a field tag PubMed ignored, a phrase it matched nothing for, a dateRange dropped for having one bound, no matches at all, or paging past the end. Absent when nothing applies."

Previous value: -"DOI"New value: +"DOI, cased as NCBI reports it. DOIs are case-insensitive by spec and no case normalization is applied here, so casing can differ from a Europe PMC-sourced `doi` — compare the two case-insensitively."

Added value: +{
+  "description": "Optional guidance when a `sections` filter removed every body section — names the requested section terms and the affected article id(s), and suggests retrying without `sections` or using broader headings. Absent when no section filter was applied or sections matched.",
+  "type": "string"
+}

Previous value: -"Article identifiers to convert. All IDs must be the same type. DOIs: \"10.1093/nar/gks1195\", PMIDs: \"23193287\", PMCIDs: \"PMC3531190\"."New value: +"Article identifiers to convert. All IDs must be the same type. DOIs: \"10.1093/nar/gks1195\", PMIDs: \"23193287\", PMCIDs: \"PMC3531190\" (the \"PMC\" prefix is optional — bare digits like \"3531190\" are also accepted)."

Previous value: -"First few hundred characters of the abstract when `resultType: \"core\"` is requested"New value: +"First few hundred characters of the abstract as display-ready plain text — JATS/HTML markup stripped and HTML entities decoded — when `resultType: \"core\"` is requested"

Added value: +{
+  "description": "NCBI Entrez UID for this record — the join key for E-utilities (eSummary/eFetch db=mesh).",
+  "type": "string"
+}

Previous value: -"MeSH descriptor unique identifier"New value: +"Canonical MeSH DescriptorUI (e.g. \"D003924\") — resolves at the MeSH Browser and NLM linked data. Falls back to the raw Entrez UID when a record is not decodable."

Previous value: -"MeSH tree numbers"New value: +"Navigable MeSH tree numbers (e.g. \"D02.078.370.141.450\"). Omitted for supplementary concept records (SCRs), which map to a heading rather than occupying a tree position."

Previous value: -[
-  "meshId",
-  "name"
-]New value: +[
+  "meshId",
+  "entrezUid",
+  "name"
+]

Removed value: -{
-  "description": "Total matching records across all pages",
-  "type": "number"
-}

Added value: +{
+  "description": "Total matching records across all pages",
+  "type": "number"
+}

Previous value: -[
-  "hits",
-  "cursorMark",
-  "searchUrl",
-  "query",
-  "hitCount",
-  "appliedSources"
-]New value: +[
+  "hits",
+  "cursorMark",
+  "searchUrl",
+  "query",
+  "totalCount",
+  "appliedSources"
+]

Added value: +{
+  "description": "Total related articles found before windowing",
+  "type": "number"
+}

Removed value: -{
-  "description": "Total related articles found before windowing",
-  "type": "number"
-}

Previous value: -[
-  "sourcePmid",
-  "relationship",
-  "offset",
-  "articles",
-  "totalFound",
-  "source"
-]New value: +[
+  "sourcePmid",
+  "relationship",
+  "offset",
+  "articles",
+  "totalCount",
+  "source"
+]

Added value: +{
+  "description": "Total matching MeSH descriptors",
+  "type": "number"
+}

Previous value: -[
-  "query",
-  "results"
-]New value: +[
+  "query",
+  "results",
+  "totalCount"
+]

Added value: +{
+  "description": "Total matching articles",
+  "type": "number"
+}

Removed value: -{
-  "description": "Total matching articles",
-  "type": "number"
-}

Previous value: -[
-  "query",
-  "offset",
-  "pmids",
-  "summaries",
-  "searchUrl",
-  "effectiveQuery",
-  "totalFound",
-  "appliedFilters"
-]New value: +[
+  "query",
+  "offset",
+  "pmids",
+  "summaries",
+  "searchUrl",
+  "effectiveQuery",
+  "totalCount",
+  "appliedFilters"
+]

Previous value: -"Optional EPMC sort: `<field> asc|desc`. Documented sortable fields: `P_PDATE_D` (publication date), `CITED` (citation count), `AUTH_FIRST` (first author surname), `PUB_YEAR` (publication year). Examples: `P_PDATE_D desc` (newest first), `CITED desc` (most cited). Omit for relevance ranking. Fields outside the documented set are rejected by EPMC."New value: +"Optional EPMC sort: `<field> asc|desc`. Documented sortable fields: `P_PDATE_D` (publication date), `CITED` (citation count), `AUTH_FIRST` (first author surname), `PUB_YEAR` (publication year). Examples: `P_PDATE_D desc` (newest first), `CITED desc` (most cited). Omit for relevance ranking. Fields outside the documented set are rejected by EPMC. Note: `P_PDATE_D` is ignored for preprint-only (`sources: [\"PPR\"]`) result sets — preprints have no populated publication date, so use `PUB_YEAR` to order preprints by date."

Added value: +{
+  "description": "Optional guidance when no articles were returned — points to discovery tools. Absent on successful fetches.",
+  "type": "string"
+}

Previous value: -"DOIs to resolve (e.g. [\"10.21203/rs.3.rs-9010375/v1\"]). Provide exactly one of `pmcids`, `pmids`, or `dois`. Covers preprints and EPMC-only OA records that lack PMID/PMCID. Chain: Europe PMC search-by-DOI → fullTextXML → Unpaywall."New value: +"DOIs to resolve (e.g. [\"10.21203/rs.3.rs-9010375/v1\"]). Provide exactly one of `pmcids`, `pmids`, or `dois`. Resolved to a PMCID via the PMC ID Converter and returned as structured JATS when the article is in PMC; DOIs with no PMC counterpart (preprints, EPMC-only OA) fall through to Europe PMC, then Unpaywall, when those layers are enabled."

Added value: +{
+  "default": 0,
+  "description": "Result offset for pagination (0-based); page through results by incrementing by maxResults",
+  "maximum": 9007199254740991,
+  "minimum": 0,
+  "type": "integer"
+}

Previous value: -"Optional guidance when results are empty — e.g. invalid source PMID, or references requested for a non-PMC source. Absent on successful result pages."New value: +"Guidance when results are empty, a fallback provider answered, or offset overshot. Absent on a clean NCBI result page."

Added value: +{
+  "description": "Result offset used",
+  "type": "number"
+}

Added value: +{
+  "description": "Provider that answered this request",
+  "enum": [
+    "ncbi",
+    "europepmc",
+    "openalex"
+  ],
+  "type": "string"
+}

Previous value: -"Total related articles found before truncation"New value: +"Total related articles found before windowing"

Previous value: -[
-  "sourcePmid",
-  "relationship",
-  "articles",
-  "totalFound"
-]New value: +[
+  "sourcePmid",
+  "relationship",
+  "offset",
+  "articles",
+  "totalFound",
+  "source"
+]

Previous value: -[
-  {
-    "description": "Single citation style. One of: apa, mla, bibtex, ris.",
-    "enum": [
-      "apa",
-      "mla",
-      "bibtex",
-      "ris"
-    ],
-    "type": "string"
-  },
-  {
-    "description": "Multiple citation styles to generate. Each entry: apa, mla, bibtex, or ris.",
-    "items": {
-      "enum": [
-        "apa",
-        "mla",
-        "bibtex",
-        "ris"
-      ],
-      "type": "string"
-    },
-    "minItems": 1,
-    "type": "array"
-  }
-]New value: +[
+  {
+    "description": "Single citation style. One of: apa, mla, bibtex, ris, vancouver.",
+    "enum": [
+      "apa",
+      "mla",
+      "bibtex",
+      "ris",
+      "vancouver"
+    ],
+    "type": "string"
+  },
+  {
+    "description": "Multiple citation styles to generate. Each entry: apa, mla, bibtex, ris, or vancouver.",
+    "items": {
+      "enum": [
+        "apa",
+        "mla",
+        "bibtex",
+        "ris",
+        "vancouver"
+      ],
+      "type": "string"
+    },
+    "minItems": 1,
+    "type": "array"
+  }
+]

Previous value: -"Citation format(s) to generate — single style as a string or multiple as an array. Allowed values: apa, mla, bibtex, ris."New value: +"Citation format(s) to generate — single style as a string or multiple as an array. Allowed values: apa, mla, bibtex, ris, vancouver."

Added value: +{
+  "description": "Optional guidance when no citations were produced — points to discovery tools. Absent when at least one citation was produced.",
+  "type": "string"
+}

Previous value: -"Citation to match against PubMed. Must include at least one bibliographic field (journal, year, volume, firstPage, or authorName)."New value: +"Citation to match against PubMed. Must include at least journal or year — ECitMatch primary-keys on journal+volume+page, so author-only or volume-only inputs guarantee no match."

Previous value: -[
-  "query",
-  "hits",
-  "hitCount",
-  "cursorMark",
-  "appliedSources",
-  "searchUrl"
-]New value: +[
+  "hits",
+  "cursorMark",
+  "searchUrl",
+  "query",
+  "hitCount",
+  "appliedSources"
+]

Previous value: -[
-  "query",
-  "effectiveQuery",
-  "appliedFilters",
-  "totalFound",
-  "offset",
-  "pmids",
-  "summaries",
-  "searchUrl"
-]New value: +[
+  "query",
+  "offset",
+  "pmids",
+  "summaries",
+  "searchUrl",
+  "effectiveQuery",
+  "totalFound",
+  "appliedFilters"
+]

Removed value: -false

Added value: +{
+  "description": "Filter by author name (e.g. \"Smith J\")",
+  "type": "string"
+}

Removed value: -false

Previous value: -"Defines an optional date range for the search."New value: +"Filter by date range"

Previous value: -"The type of date to filter by: 'pdat' (Publication Date), 'mdat' (Modification Date), 'edat' (Entrez Date). Default is 'pdat'."New value: +"Date type: pdat (publication), mdat (modification), edat (entrez)"

Previous value: -"The end date for the search range (YYYY, YYYY/MM, or YYYY/MM/DD)."New value: +"End date (YYYY/MM/DD, YYYY/MM, or YYYY)"

Removed value: -"^\\d{4}(\\/\\d{2}(\\/\\d{2})?)?$"

Previous value: -"The start date for the search range (YYYY, YYYY/MM, or YYYY/MM/DD)."New value: +"Start date (YYYY/MM/DD, YYYY/MM, or YYYY)"

Removed value: -"^\\d{4}(\\/\\d{2}(\\/\\d{2})?)?$"

Added value: +[
+  "minDate",
+  "maxDate"
+]

Removed value: -{
-  "default": 0,
-  "description": "Number of top PMIDs for which to fetch brief summaries using ESummary. Set to 0 to disable. Max 50. Default 0.",
-  "maximum": 50,
-  "minimum": 0,
-  "type": "integer"
-}

Removed value: -{
-  "description": "An array of publication types to filter by (e.g., [\"Review\", \"Clinical Trial\"]).",
-  "items": {
-    "type": "string"
-  },
-  "type": "array"
-}

Added value: +{
+  "description": "Only include free full text articles",
+  "type": "boolean"
+}

Added value: +{
+  "description": "Only include articles with abstracts",
+  "type": "boolean"
+}

Added value: +{
+  "description": "Filter by journal name",
+  "type": "string"
+}

Added value: +{
+  "description": "Filter by language (e.g. \"english\")",
+  "type": "string"
+}

Previous value: -"Maximum number of articles to retrieve. Corresponds to ESearch's 'retmax' parameter. Default is 20, max is 1000."New value: +"Maximum results to return"

Removed value: -0

Added value: +1

Added value: +{
+  "description": "Filter by MeSH terms",
+  "items": {
+    "type": "string"
+  },
+  "type": "array"
+}

Added value: +{
+  "default": 0,
+  "description": "Result offset for pagination (0-based)",
+  "maximum": 9007199254740991,
+  "minimum": 0,
+  "type": "integer"
+}

Added value: +{
+  "description": "Filter by publication type (e.g. \"Review\", \"Clinical Trial\", \"Meta-Analysis\")",
+  "items": {
+    "type": "string"
+  },
+  "type": "array"
+}

Added value: +{
+  "description": "PubMed search query (supports full NCBI syntax)",
+  "minLength": 1,
+  "type": "string"
+}

Removed value: -{
-  "description": "The primary keyword or phrase to search for in PubMed. Must be at least 3 characters long.",
-  "minLength": 3,
-  "type": "string"
-}

Added value: +{
+  "default": "relevance",
+  "description": "Sort order: relevance (default), pub_date (newest first), author, or journal",
+  "enum": [
+    "relevance",
+    "pub_date",
+    "author",
+    "journal"
+  ],
+  "type": "string"
+}

Removed value: -{
-  "default": "relevance",
-  "description": "Sorting criteria for results. Options: 'relevance' (default), 'pub_date', 'author', 'journal_name'.",
-  "enum": [
-    "relevance",
-    "pub_date",
-    "author",
-    "journal_name"
-  ],
-  "type": "string"
-}

Added value: +{
+  "description": "Filter by species",
+  "enum": [
+    "humans",
+    "animals"
+  ],
+  "type": "string"
+}

Added value: +{
+  "default": 0,
+  "description": "Fetch brief summaries for top N results (0 = PMIDs only)",
+  "maximum": 50,
+  "minimum": 0,
+  "type": "integer"
+}

Previous value: -[
-  "queryTerm"
-]New value: +[
+  "query"
+]

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "offset": {
+      "description": "Result offset used",
+      "type": "number"
+    },
+    "pmids": {
+      "description": "PubMed IDs",
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "query": {
+      "description": "Original query",
+      "type": "string"
+    },
+    "searchUrl": {
+      "description": "PubMed search URL",
+      "type": "string"
+    },
+    "summaries": {
+      "description": "Brief summaries (empty array when summaryCount is 0)",
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "authors": {
+            "description": "Formatted author string",
+            "type": "string"
+          },
+          "doi": {
+            "description": "DOI",
+            "type": "string"
+          },
+          "pmcId": {
+            "description": "PMC ID",
+            "type": "string"
+          },
+          "pmcUrl": {
+            "description": "PMC URL",
+            "type": "string"
+          },
+          "pmid": {
+            "description": "PubMed ID",
+            "type": "string"
+          },
+          "pubDate": {
+            "description": "Publication date",
+            "type": "string"
+          },
+          "pubmedUrl": {
+            "description": "PubMed URL",
+            "type": "string"
+          },
+          "source": {
+            "description": "Journal source",
+            "type": "string"
+          },
+          "title": {
+            "description": "Article title",
+            "type": "string"
+          }
+        },
+        "required": [
+          "pmid"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "totalFound": {
+      "description": "Total matching articles",
+      "type": "number"
+    }
+  },
+  "required": [
+    "query",
+    "totalFound",
+    "offset",
+    "pmids",
+    "summaries",
+    "searchUrl"
+  ],
+  "type": "object"
+}