# `crossref__crossref_search_works`
**Search Works**
Searches the Crossref works index (~155M records) by free text and/or structured filters. The generic query matches loosely across all fields; scope precisely with the field-specific parameters queryTitle, queryAuthor, and queryContainerTitle, or resolve a known citation to its DOI with queryBibliographic — all combine with each other and with query. Use the filter parameter for structured filtering (object with hyphen-separated Crossref keys). Sort options: relevance, score, is-referenced-by-count, published, deposited, indexed. Each work returns at most authorLimit authors (25 by default) with authorCount reporting the full deposited total, since a single page of large-collaboration papers can carry tens of thousands of author entries; crossref_get_work pages the whole author list for any DOI whose list was cut. Offset-based paging is capped at ~10K results; use cursor="*" to start cursor-based deep paging, then pass the nextCursor value from each response to continue. The walk ends on the page where nextCursor is absent — that page also carries a notice saying the list is exhausted. Cursor and offset cannot be combined.
- Server: [Crossref](https://gateway.mcpharbor.dev/docs/servers/crossref) (`dev.mcpharbor.gateway/crossref`)
- Price per call: $0.0001 (100 micro-USD); only tools/call is charged
- Endpoint: `https://gateway.mcpharbor.dev/mcp` or `https://gateway.mcpharbor.dev/mcp/crossref`
- Upstream tool: exposed by the provider; called through this gateway as `crossref__crossref_search_works`
- Provider terms: (verified 2026-09-19)
- Upstream API documentation:
- Rate limit: 50 requests per minute
## Parameters
- `authorLimit` (integer, optional): Maximum number of authors to return per work (1–500, default 25). Ordinary records fit under the default; large-collaboration papers deposit thousands, and a page of them is large enough to exhaust... Default: `25`.
- `cursor` (string, optional): Cursor token for deep paging. Pass "*" to start cursor-based paging (required past ~10K results), then pass the nextCursor value from each response until a response omits it, which means the list i...
- `fields` (array, optional): Fields to return (reduces payload). Names are case-sensitive. Useful set: DOI, title, author, published, type, is-referenced-by-count, abstract, container-title, publisher, score. DOI is always ret...
- `filter` (object, optional): Structured filter object using Crossref hyphen-separated keys. All values must be strings. Boolean flag keys (has-abstract, has-references, has-full-text) require string values "true" or "false". E...
- `offset` (number, optional): Zero-based result offset for offset-based paging. Cannot be used with cursor. Capped at ~10K; use cursor for deeper paging.
- `order` (string, optional): Sort direction (asc or desc) One of: `asc`, `desc`.
- `query` (string, optional): Free-text search query, e.g. "CRISPR gene editing" or "climate change adaptation"
- `queryAuthor` (string, optional): Match against author names only, e.g. "Charles R. Harris".
- `queryBibliographic` (string, optional): Whole-citation match to resolve a known reference to its DOI. Combine title, author, year, and container into one string, e.g. "Watson Crick molecular structure of nucleic acids Nature 1953".
- `queryContainerTitle` (string, optional): Match against the container title (journal or book name) only, e.g. "Nature".
- `queryTitle` (string, optional): Match against work titles only, e.g. "Array programming with NumPy".
- `rows` (number, optional): Number of results to return per page (1–100, default 20) Default: `20`.
- `sort` (string, optional): Sort field One of: `relevance`, `score`, `is-referenced-by-count`, `published`, `published-print`, `published-online`, `deposited`, `indexed`, `created`, `updated`, `references-count`.
## Example call
Request headers and body:
```http
POST /mcp HTTP/1.1
Host: gateway.mcpharbor.dev
Authorization: Bearer
Content-Type: application/json
Accept: application/json, text/event-stream
MCP-Protocol-Version: 2026-07-28
Mcp-Method: tools/call
Mcp-Name: crossref__crossref_search_works
```
```json
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"_meta": {
"io.modelcontextprotocol/clientCapabilities": {},
"io.modelcontextprotocol/clientInfo": {
"name": "example-agent",
"version": "1.0.0"
},
"io.modelcontextprotocol/protocolVersion": "2026-07-28"
},
"arguments": {
"authorLimit": 1
},
"name": "crossref__crossref_search_works"
}
}
```
A successful response:
```json
{
"id": 1,
"jsonrpc": "2.0",
"result": {
"_meta": {
"dev.mcpharbor.gateway/call": {
"chargedMicroUsd": 100,
"id": ""
}
},
"content": [
{
"text": "",
"type": "text"
}
],
"resultType": "complete"
}
}
```
This call costs $0.0001 (100 micro-USD). Reading this page and listing the tool cost nothing.
The `dev.mcpharbor.gateway/call` record in the result is the receipt for that charge. Each
POST is metered separately, so sending the same call again buys another one: see
[agent.txt](https://gateway.mcpharbor.dev/agent.txt), section 7, before retrying.
## Attribution
This provider asks for no attribution. Their terms still apply: see the table above.
## Tool definition
Exactly as `tools/list` returns it (free):
```json
{
"_meta": {
"dev.mcpharbor.gateway/pricing": {
"currency": "USD",
"pricePerCallMicroUsd": 100
}
},
"annotations": {
"openWorldHint": true,
"readOnlyHint": true
},
"description": "Searches the Crossref works index (~155M records) by free text and/or structured filters. The generic query matches loosely across all fields; scope precisely with the field-specific parameters queryTitle, queryAuthor, and queryContainerTitle, or resolve a known citation to its DOI with queryBibliographic — all combine with each other and with query. Use the filter parameter for structured filtering (object with hyphen-separated Crossref keys). Sort options: relevance, score, is-referenced-by-count, published, deposited, indexed. Each work returns at most authorLimit authors (25 by default) with authorCount reporting the full deposited total, since a single page of large-collaboration papers can carry tens of thousands of author entries; crossref_get_work pages the whole author list for any DOI whose list was cut. Offset-based paging is capped at ~10K results; use cursor=\"*\" to start cursor-based deep paging, then pass the nextCursor value from each response to continue. The walk ends on the page where nextCursor is absent — that page also carries a notice saying the list is exhausted. Cursor and offset cannot be combined.",
"inputSchema": {
"$schema": "https://json-schema.org/draft/2020-12/schema",
"additionalProperties": false,
"properties": {
"authorLimit": {
"default": 25,
"description": "Maximum number of authors to return per work (1–500, default 25). Ordinary records fit under the default; large-collaboration papers deposit thousands, and a page of them is large enough to exhaust a client context. Each work reports its full deposited total as authorCount — call crossref_get_work with that work doi to page the authors this cap left out.",
"maximum": 500,
"minimum": 1,
"type": "integer"
},
"cursor": {
"description": "Cursor token for deep paging. Pass \"*\" to start cursor-based paging (required past ~10K results), then pass the nextCursor value from each response until a response omits it, which means the list is exhausted. Cannot be combined with offset.",
"type": "string"
},
"fields": {
"description": "Fields to return (reduces payload). Names are case-sensitive. Useful set: DOI, title, author, published, type, is-referenced-by-count, abstract, container-title, publisher, score. DOI is always returned whether or not it is listed here, so every result stays resolvable by crossref_get_work.",
"items": {
"type": "string"
},
"type": "array"
},
"filter": {
"additionalProperties": {
"type": "string"
},
"description": "Structured filter object using Crossref hyphen-separated keys. All values must be strings. Boolean flag keys (has-abstract, has-references, has-full-text) require string values \"true\" or \"false\". Example: {\"type\":\"journal-article\",\"has-abstract\":\"true\",\"from-pub-date\":\"2023-01-01\",\"directory\":\"DOAJ\"}",
"propertyNames": {
"type": "string"
},
"type": "object"
},
"offset": {
"description": "Zero-based result offset for offset-based paging. Cannot be used with cursor. Capped at ~10K; use cursor for deeper paging.",
"minimum": 0,
"type": "number"
},
"order": {
"description": "Sort direction (asc or desc)",
"enum": [
"asc",
"desc"
],
"type": "string"
},
"query": {
"description": "Free-text search query, e.g. \"CRISPR gene editing\" or \"climate change adaptation\"",
"type": "string"
},
"queryAuthor": {
"description": "Match against author names only, e.g. \"Charles R. Harris\".",
"type": "string"
},
"queryBibliographic": {
"description": "Whole-citation match to resolve a known reference to its DOI. Combine title, author, year, and container into one string, e.g. \"Watson Crick molecular structure of nucleic acids Nature 1953\".",
"type": "string"
},
"queryContainerTitle": {
"description": "Match against the container title (journal or book name) only, e.g. \"Nature\".",
"type": "string"
},
"queryTitle": {
"description": "Match against work titles only, e.g. \"Array programming with NumPy\".",
"type": "string"
},
"rows": {
"default": 20,
"description": "Number of results to return per page (1–100, default 20)",
"maximum": 100,
"minimum": 1,
"type": "number"
},
"sort": {
"description": "Sort field",
"enum": [
"relevance",
"score",
"is-referenced-by-count",
"published",
"published-print",
"published-online",
"deposited",
"indexed",
"created",
"updated",
"references-count"
],
"type": "string"
}
},
"type": "object"
},
"name": "crossref__crossref_search_works",
"outputSchema": {
"$schema": "https://json-schema.org/draft/2020-12/schema",
"additionalProperties": false,
"anyOf": [
{
"not": {
"required": [
"error"
]
},
"required": [
"works",
"totalResults",
"returned"
]
},
{
"required": [
"error"
]
}
],
"properties": {
"cap": {
"description": "The per-work author cap applied to this page. Absent when no list was cut.",
"type": "number"
},
"error": {
"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: `rate_limited`: Crossref answered HTTP 429 and the limit did not clear inside the retry budget. `upstream_unavailable`: Crossref was unreachable, returned a 5xx status, or served an HTML error page instead of JSON. `malformed_response`: Crossref returned HTTP 200 with a body that is not valid JSON. `request_timeout`: Crossref did not respond within CROSSREF_TIMEOUT_MS, or answered HTTP 408/504. `cursor_offset_conflict`: Both cursor and offset were supplied in the same request. `offset_too_large`: The requested offset exceeds the ~10K Crossref limit for offset-based paging. Other values are possible when a failure originates below the handler.",
"examples": [
"rate_limited",
"upstream_unavailable",
"malformed_response",
"request_timeout",
"cursor_offset_conflict",
"offset_too_large"
],
"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"
},
"nextCursor": {
"description": "Cursor token to pass as cursor on the next call to continue a cursor walk. Present only on a page requested with cursor, and absent once the walk reaches the end of the list.",
"type": "string"
},
"notice": {
"description": "Guidance on an empty page, naming which of its three causes applies: a query nothing matched, an offset past the end of a list that did match, or a cursor walk that has reached the end of the list. On a page carrying records, present only when authorLimit cut at least one work list, naming how many and the route to the rest.",
"type": "string"
},
"returned": {
"description": "Number of records returned in this response",
"type": "number"
},
"totalResults": {
"description": "Total matching records in Crossref",
"type": "number"
},
"truncated": {
"description": "True when at least one work on this page had its author list cut by authorLimit. Absent when every work on the page carries its full deposited author list.",
"type": "boolean"
},
"works": {
"description": "Matching works. Empty when nothing matched the query, when an offset runs past the end of the results, or on the page that ends a cursor walk — the notice enrichment says which.",
"items": {
"additionalProperties": false,
"description": "Work summary",
"properties": {
"abstract": {
"description": "Abstract when present in the indexed record — the text of the publisher’s JATS deposit, with markup removed and character references decoded; a link keeps its tag only where its href holds an address the text it wraps does not already carry, and a formula the deposit encodes more than once appears once, in the first notation deposited",
"type": "string"
},
"authorCount": {
"description": "Total number of authors deposited for this work, before the authorLimit cap. Greater than the length of authors when the cap cut the list; pass the doi of this work to crossref_get_work to page the whole list.",
"type": "number"
},
"authors": {
"description": "Author list for this work, capped at authorLimit. Omitted when the record deposits no author field.",
"items": {
"additionalProperties": false,
"description": "Author",
"properties": {
"family": {
"description": "Family name",
"type": "string"
},
"given": {
"description": "Given name",
"type": "string"
},
"name": {
"description": "Name when no given/family split is available",
"type": "string"
}
},
"type": "object"
},
"type": "array"
},
"containerTitle": {
"description": "Journal or container name",
"type": "string"
},
"doi": {
"description": "Canonical DOI",
"type": "string"
},
"isReferencedByCount": {
"description": "Incoming citation count",
"type": "number"
},
"published": {
"additionalProperties": false,
"description": "Publication date — the first of published, published-print, and published-online that names one. A component Crossref records as unknown is omitted, and so is every component below it.",
"properties": {
"day": {
"description": "Day",
"type": "number"
},
"month": {
"description": "Month",
"type": "number"
},
"year": {
"description": "Year",
"type": "number"
}
},
"type": "object"
},
"publisher": {
"description": "Publisher name",
"type": "string"
},
"score": {
"description": "Relevance score assigned by Crossref",
"type": "number"
},
"title": {
"description": "Work title",
"type": "string"
},
"type": {
"description": "Work type",
"type": "string"
}
},
"required": [
"doi"
],
"type": "object"
},
"type": "array"
}
},
"type": "object"
},
"title": "Search Works"
}
```