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: -"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."

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

Added value: +"Parsed PubMed article"

Added value: +"Dated article event"

Added value: +"Author record"

Added value: +"Grant record"

Added value: +"MeSH descriptor term"

Added value: +"MeSH qualifier/subheading"