# `crossref__crossref_get_references`
**Get Reference List**
Returns the outgoing reference list for a DOI — the works cited by this paper. Each reference includes the deposited citation string and, where Crossref has resolved it, a DOI you can look up with crossref_get_work. Results are paged: referenceCount is the full deposited total, and when more remain the response carries a nextOffset to pass back as offset. Reference list coverage varies by publisher; many older works and non-participating publishers have no indexed references. Incoming citations — the works that cite this paper — are not available through Crossref; use OpenAlex for that.
- 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_get_references`
- Provider terms: (verified 2026-09-19)
- Upstream API documentation:
- Rate limit: 50 requests per minute
## Parameters
- `doi` (string, required): DOI in the format "10.NNNN/suffix", e.g. "10.1038/nature12373". Must start with "10." followed by 4–9 digits and a slash.
- `limit` (integer, optional): Maximum number of references to return in one page (1–500, default 100). Most works fit in a single page; bibliography records can carry tens of thousands. Default: `100`.
- `offset` (integer, optional): Zero-based index of the first reference to return. Pass the nextOffset value from the previous response to continue through a long reference list. Default: `0`.
## 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_get_references
```
```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": {
"doi": "example"
},
"name": "crossref__crossref_get_references"
}
}
```
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 $0.0001 (100 micro-USD). Reading this page and listing the tool cost nothing.
The `dev.mcpharbor.gateway/call` record in the result is the receipt for that charge. Each
POST is metered separately, so sending the same call again buys another one: see
[agent.txt](https://gateway.mcpharbor.dev/agent.txt), section 7, before retrying.
## Attribution
This provider asks for no attribution. Their terms still apply: see the table above.
## Tool definition
Exactly as `tools/list` returns it (free):
```json
{
"_meta": {
"dev.mcpharbor.gateway/pricing": {
"currency": "USD",
"pricePerCallMicroUsd": 100
}
},
"annotations": {
"idempotentHint": true,
"readOnlyHint": true
},
"description": "Returns the outgoing reference list for a DOI — the works cited by this paper. Each reference includes the deposited citation string and, where Crossref has resolved it, a DOI you can look up with crossref_get_work. Results are paged: referenceCount is the full deposited total, and when more remain the response carries a nextOffset to pass back as offset. Reference list coverage varies by publisher; many older works and non-participating publishers have no indexed references. Incoming citations — the works that cite this paper — are not available through Crossref; use OpenAlex for that.",
"inputSchema": {
"$schema": "https://json-schema.org/draft/2020-12/schema",
"additionalProperties": false,
"properties": {
"doi": {
"description": "DOI in the format \"10.NNNN/suffix\", e.g. \"10.1038/nature12373\". Must start with \"10.\" followed by 4–9 digits and a slash.",
"pattern": "^10\\.\\d{4,9}\\/\\S+$",
"type": "string"
},
"limit": {
"default": 100,
"description": "Maximum number of references to return in one page (1–500, default 100). Most works fit in a single page; bibliography records can carry tens of thousands.",
"maximum": 500,
"minimum": 1,
"type": "integer"
},
"offset": {
"default": 0,
"description": "Zero-based index of the first reference to return. Pass the nextOffset value from the previous response to continue through a long reference list.",
"maximum": 9007199254740991,
"minimum": 0,
"type": "integer"
}
},
"required": [
"doi"
],
"type": "object"
},
"name": "crossref__crossref_get_references",
"outputSchema": {
"$schema": "https://json-schema.org/draft/2020-12/schema",
"additionalProperties": false,
"anyOf": [
{
"not": {
"required": [
"error"
]
},
"required": [
"doi",
"referenceCount",
"offset",
"references"
]
},
{
"required": [
"error"
]
}
],
"properties": {
"cap": {
"description": "The limit that was applied to this page.",
"type": "number"
},
"doi": {
"description": "DOI of the citing work",
"type": "string"
},
"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. `doi_not_found`: Valid DOI format but no Crossref record exists. Other values are possible when a failure originates below the handler.",
"examples": [
"rate_limited",
"upstream_unavailable",
"malformed_response",
"request_timeout",
"doi_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"
},
"nextOffset": {
"description": "Offset to pass in the next call to retrieve the following page. Absent when this page reaches the end of the reference list.",
"type": "number"
},
"notice": {
"description": "Coverage guidance when no references are indexed, or a range explanation when the requested offset is past the end of the list. Absent on a normal page.",
"type": "string"
},
"offset": {
"description": "Zero-based index of the first returned reference within the deposited list",
"type": "number"
},
"referenceCount": {
"description": "Total number of references in the deposited list",
"type": "number"
},
"references": {
"description": "Page of the outgoing reference list",
"items": {
"additionalProperties": false,
"description": "Reference entry",
"properties": {
"articleTitle": {
"description": "Article title of the referenced work, with inline formatting markup removed",
"type": "string"
},
"author": {
"description": "Author field from the reference entry, with inline formatting markup removed",
"type": "string"
},
"doi": {
"description": "Resolved DOI for this reference, when available",
"type": "string"
},
"firstPage": {
"description": "First page",
"type": "string"
},
"issn": {
"description": "ISSN of the referenced journal",
"type": "string"
},
"journalTitle": {
"description": "Journal title of the referenced work, with inline formatting markup removed",
"type": "string"
},
"key": {
"description": "Reference key as deposited",
"type": "string"
},
"unstructured": {
"description": "Citation string as deposited by the publisher, with formatting markup and structured-citation tags removed. Angle-bracketed text that is not recognizable as markup — a cited URL, a Miller index, a DOI fragment — is left exactly as deposited, and so is a link whose href holds an address the text it wraps does not already carry.",
"type": "string"
},
"volume": {
"description": "Volume",
"type": "string"
},
"year": {
"description": "Publication year of the referenced work",
"type": "string"
}
},
"type": "object"
},
"type": "array"
},
"shown": {
"description": "Number of references returned in this page.",
"type": "number"
},
"truncated": {
"description": "True when references remain beyond this page. Absent when the page is the last.",
"type": "boolean"
}
},
"type": "object"
},
"title": "Get Reference List"
}
```