Previous 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."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), `FIRST_IDATE_D` (date first indexed in Europe PMC). Examples: `P_PDATE_D desc` (newest first), `CITED desc` (most cited). Omit for relevance ranking; `relevance` or `relevance desc` is sent as no sort. Field and direction match case-insensitively. Each key must be one field plus `asc` or `desc`: a key without a direction, an empty key, or an extra word fails with `europepmc_invalid_input` before the request. A field outside the documented set may be honored, silently ignored, or refused — a sort Europe PMC refuses fails with `europepmc_invalid_input` naming it, and an empty Europe PMC response to a sort with an undocumented field fails the same way, 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 desc` to order preprints by date."

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 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."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; a sort it cannot use (one whose keys are not each a field plus asc/desc, rejected before any request; an empty response to a sort with an undocumented field; or a second HTTP 503 to a sorted search when the same query without the sort is served); 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: -"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."New value: +"Whether `abstractSnippet` was cut short of the full abstract. Retrieve the complete text by passing this record to `pubmed_europepmc_fetch` as `records: [{ source, epmcId }]`. Present whenever `abstractSnippet` is; omitted when Europe PMC carries no abstract."

Previous 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."New value: +"Europe PMC's internal record id. Pass it with this hit's `source` to `pubmed_europepmc_fetch` as `records: [{ source, epmcId }]` 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: -"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"
+]

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: -[
-  {
-    "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: -"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: -"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: -"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."

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: -"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: -"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: -"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: -"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 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"

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"
+]

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."

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

Previous value: -"Optional EPMC sort spec, e.g. `FIRST_PIDATE desc` (newest first) or `CITED desc` (most cited). Omit for relevance order."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."