# Crossref API

> Crossref returns formatted citations and publication details as a workflow and API.

Get citation returns citation and publication details for a title or DOI; optional author and year help match the work.

- Page: https://fous.com/tools/crossref
- Handle: `@crossref`
- Category: [Science](https://fous.com/tools/category/science)
- Source website: https://crossref.org
- Last verified: Sep 29, 2026

## Methods

### Get citation

Operation `get_citation`, version 1. 1 credit per completed call. Failed calls without a completed billing receipt are free; completed work can remain charged if delivery is interrupted.

Get a formatted citation and publication details for the best-matching Crossref work by title or DOI. Optional author and year help choose among similar works; citations reflect the metadata deposited with Crossref.

**Input**

| Field | Type | Required | Example | Description |
|---|---|---|---|---|
| `work` | string | yes | `"The Structure of Scientific Revolutions"` | Paper or book title or DOI, for example The Structure of Scientific Revolutions or 10.1038/nrd842. |
| `year` | integer | no | `1996` | Publication year to help select a work, for example 1996. |
| `style` | string | no | `"apa"` | Citation style, for example mla. |
| `author` | string | no | `"Thomas S. Kuhn"` | Author to help select a work, for example Thomas S. Kuhn. |

**Input schema**

```json
{
  "type": "object",
  "required": [
    "work"
  ],
  "properties": {
    "work": {
      "type": "string",
      "description": "Paper or book title or DOI, for example The Structure of Scientific Revolutions or 10.1038/nrd842.",
      "examples": [
        "The Structure of Scientific Revolutions",
        "10.1038/nrd842"
      ]
    },
    "year": {
      "type": "integer",
      "description": "Publication year to help select a work, for example 1996.",
      "examples": [
        1996,
        2012
      ]
    },
    "style": {
      "enum": [
        "apa",
        "mla",
        "chicago",
        "harvard",
        "ieee",
        "vancouver"
      ],
      "type": "string",
      "default": "apa",
      "description": "Citation style, for example mla.",
      "examples": [
        "apa",
        "mla",
        "chicago"
      ]
    },
    "author": {
      "type": "string",
      "default": "",
      "description": "Author to help select a work, for example Thomas S. Kuhn.",
      "examples": [
        "Thomas S. Kuhn"
      ]
    }
  },
  "additionalProperties": false,
  "examples": [
    {
      "work": "The Structure of Scientific Revolutions",
      "year": 1996,
      "style": "apa",
      "author": "Thomas S. Kuhn"
    },
    {
      "work": "10.1038/nrd842",
      "style": "mla"
    },
    {
      "work": "The Structure of Scientific Revolutions",
      "year": 2012,
      "style": "chicago",
      "author": "Thomas S. Kuhn"
    }
  ]
}
```

**Output**

| Field | Type | Example | Description |
|---|---|---|---|
| `doi` | string | `"10.7208/chicago/9780226458106.001.0001"` |  |
| `type` | string or null | `"book"` |  |
| `year` | integer or null | `1996` |  |
| `issue` | string or null | `"7"` |  |
| `pages` | string or null | `"491-492"` |  |
| `title` | string or null | `"The Structure of Scientific Revolutions"` |  |
| `volume` | string or null | `"1"` |  |
| `authors` | array |  |  |
| `citation` | string | `"Kuhn, T. S. (1996). The Structure of Scientific Revolutions. University of Chicago Press. https://doi.org/10.7208/chica` |  |
| `doi_link` | string | `"https://doi.org/10.7208/chicago/9780226458106.001.0001"` |  |
| `journal_or_publisher` | string or null | `"University of Chicago Press"` |  |

**Example input**

```json
{
  "work": "The Structure of Scientific Revolutions",
  "year": 1996,
  "style": "apa",
  "author": "Thomas S. Kuhn"
}
```

**Example output**

```json
{
  "doi": "10.7208/chicago/9780226458106.001.0001",
  "type": "book",
  "year": 1996,
  "issue": null,
  "pages": null,
  "title": "The Structure of Scientific Revolutions",
  "volume": null,
  "authors": [
    "Thomas S. Kuhn"
  ],
  "citation": "Kuhn, T. S. (1996). The Structure of Scientific Revolutions. University of Chicago Press. https://doi.org/10.7208/chicago/9780226458106.001.0001",
  "doi_link": "https://doi.org/10.7208/chicago/9780226458106.001.0001",
  "journal_or_publisher": "University of Chicago Press"
}
```

## Quick start

Replace `YOUR_API_KEY` with a Fous API key. To create one, open Developers at the bottom of Fous Studio, turn on Developer mode, then go to API keys (https://app.fous.com/keys). Change the values in `input` to run the same tool on new data.

```bash
curl 'https://api.fous.com/v1/query' \
  --fail-with-body --silent --show-error --max-time 180 \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H 'Content-Type: application/json' \
  --data-raw '{
  "api": "@crossref",
  "visibility": "public",
  "operation": "get_citation",
  "version": 1,
  "input": {
    "work": "The Structure of Scientific Revolutions",
    "year": 1996,
    "style": "apa",
    "author": "Thomas S. Kuhn"
  },
  "response": {
    "format": "json"
  }
}'
```

```python
# Save as fous.py and run with python3 fous.py. No packages needed.
import json
import urllib.error
import urllib.request

api_key = "YOUR_API_KEY"

body = json.loads("{\n  \"api\": \"@crossref\",\n  \"visibility\": \"public\",\n  \"operation\": \"get_citation\",\n  \"version\": 1,\n  \"input\": {\n    \"work\": \"The Structure of Scientific Revolutions\",\n    \"year\": 1996,\n    \"style\": \"apa\",\n    \"author\": \"Thomas S. Kuhn\"\n  },\n  \"response\": {\n    \"format\": \"json\"\n  }\n}")
request = urllib.request.Request(
    "https://api.fous.com/v1/query",
    data=json.dumps(body).encode("utf-8"),
    headers={
        "Authorization": f"Bearer {api_key}",
        "Content-Type": "application/json",
    },
    method="POST",
)
try:
    with urllib.request.urlopen(request, timeout=180) as response:
        result = json.load(response)
except urllib.error.HTTPError as error:
    raise RuntimeError(f"HTTP {error.code}: {error.read().decode('utf-8', errors='replace')}") from error
if result.get("success") is False:
    raise RuntimeError(result.get("error", {}).get("message", "Request failed"))
print(json.dumps(result["data"]["output"], indent=2))
```

```typescript
// Save as fous.mts and run with npx tsx fous.mts.
const apiKey = "YOUR_API_KEY";

const response = await fetch("https://api.fous.com/v1/query", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${apiKey}`,
    "Content-Type": "application/json",
  },
  signal: AbortSignal.timeout(180_000),
  body: JSON.stringify({
  "api": "@crossref",
  "visibility": "public",
  "operation": "get_citation",
  "version": 1,
  "input": {
    "work": "The Structure of Scientific Revolutions",
    "year": 1996,
    "style": "apa",
    "author": "Thomas S. Kuhn"
  },
  "response": {
    "format": "json"
  }
}),
});
type ApiResult = { success: boolean; data?: { output: unknown }; error?: { message: string } };
const result: ApiResult = await response.json();
if (!response.ok || result.success === false) {
  throw new Error(result.error?.message ?? `HTTP ${response.status}`);
}
if (!result.data) throw new Error("Missing API response data");
console.log(result.data.output);
```

## Use from an AI assistant

Connect this tool to Claude Code, Claude Desktop, Cursor, VS Code, Codex and any MCP client as its own MCP server. Each method is a typed tool whose arguments are the method’s input.

- Server URL: `https://api.fous.com/mcp/tools/crossref`
- Authorization: `Authorization: Bearer <Fous API key>`

**Tools**

- `get_citation`: Get citation. 1 credit per completed call. Failed calls without a completed billing receipt are free; completed work can remain charged if delivery is interrupted.
- `fous_get_run`: the result of a run that was still going, by its `request_id`. Free.

Claude Code:

```bash
claude mcp add --scope user --transport http fous-crossref https://api.fous.com/mcp/tools/crossref --header "Authorization: Bearer ${FOUS_API_KEY:?Set FOUS_API_KEY to your Fous API key}"
```

To give the assistant every tool, connect `https://api.fous.com/mcp`: it finds one with `fous_search_tools` and runs it with `fous_run_tool`. Setup for other clients: https://fous.com/llms-full.txt.

## Use cases

- Create formatted citations for papers and books
- Look up publication details from a DOI
- Match a work using its title, author, and year
- Format citations in a chosen style

## FAQ

### Can I run it with my own inputs?

Yes. Change the inputs in Studio and press Run, or send new inputs from your code, or ask a connected AI assistant.

### Can I call this Crossref tool as an API?

Yes. Send a POST request to /v1/query with your Fous API key and the inputs, and get JSON back.

### How much does it cost?

Each completed run costs 1 credit. Failed runs without a completed receipt are free; completed work can remain charged if delivery is interrupted. With pay as you go, a credit costs 1¢. Monthly plans cost less per credit.

### Do I need a Crossref account?

No. You only need a Fous account.

### How current is the data?

Fous gets the data from crossref.org when you run it. Some results are reused for up to 24 hours, and results that use your account or key are never reused. It was last verified on Sep 29, 2026.

### How can I get a citation for a paper title?

Use Get citation with the paper title; add an author or year to help match the work.

### What publication details are available for a DOI?

Get citation accepts a DOI and returns details such as the title, authors, year, journal or publisher, and pages.

### Can I choose a citation style?

Yes. Get citation accepts a style, such as mla, to format the citation.

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- [All Science tools](https://fous.com/tools/category/science)