# Crossref Citation MCP Server (`nexgenwatch/crossref-citation-mcp`) Actor

An MCP server over the official Crossref REST API (api.crossref.org) — scholarly work

- **URL**: https://apify.com/nexgenwatch/crossref-citation-mcp.md
- **Developed by:** [NexGen Watch](https://apify.com/nexgenwatch) (community)
- **Categories:** Developer tools
- **Stats:** 1 total users, 0 monthly users, 0.0% runs succeeded, 0 bookmarks
- **User rating**: No ratings yet

## Pricing

from $50.00 / 1,000 tool calls

This Actor is paid per event and usage. You are charged both the fixed price for specific events and for Apify platform usage.

Learn more: https://docs.apify.com/actors/running/actors-in-store.md#pay-per-event

## What's an Apify Actor?

Actors are web data automations that power AI and operations. They run on the Apify platform to scrape websites, process data, connect APIs, and automate workflows.
In Batch mode, an Actor accepts a well-defined JSON input, performs an action which can take anything from a few seconds to a few hours,
and optionally produces a well-defined JSON output, datasets with results, or files in key-value store.
In Standby mode, an Actor provides a web server which can be used as a website, API, or an MCP server.
Actors are written with capital "A".

## How to integrate an Actor?

If asked about integration, you help developers integrate Actors into their projects.
You adapt to their stack and deliver integrations that are safe, well-documented, and production-ready.
The best way to integrate Actors is as follows.

- **AI agents and MCP clients** — the [Apify MCP server](https://docs.apify.com/integrations/mcp.md) at `https://mcp.apify.com` (remote, streamable HTTP, OAuth on first use).
- **Agentic workflows and local Actor development** — [Agent Skills](https://apify.com/.well-known/agent-skills/index.json) with the [Apify CLI](https://docs.apify.com/cli/docs.md): `npm install -g apify-cli`, then `apify login`.
- **JavaScript/TypeScript projects** — the official [JS/TS client](https://docs.apify.com/api/client/js/docs.md): `npm install apify-client`.
- **Python projects** — the official [Python client](https://docs.apify.com/api/client/python/docs.md): `pip install apify-client`.
- **Any other language** — the [REST API](https://docs.apify.com/api/v2.md).

For usage examples, see the [API](#api) section below.

For more details, see Apify documentation as [Markdown index](https://docs.apify.com/llms.txt) and [Markdown full-text](https://docs.apify.com/llms-full.txt).

# README

## Crossref Citation MCP Server

An MCP server over the **official Crossref REST API** (`api.crossref.org`) — scholarly work
metadata and citation counts across registered publishers. Runs as an Apify **Standby** MCP
server; connect an MCP client to the server URL at path `/mcp`.

### Tools

- `search_works(query, rows)` — search Crossref by free text; returns DOIs, titles, years and citation counts.
- `get_work(doi)` — full metadata for one DOI: title, authors, journal, year, publisher, citation and reference counts.
- `get_citation_count(doi)` — how many works Crossref records as citing this DOI (`is-referenced-by-count`).
- `explain_limits()` — scope, the meaning of the citation count, and what the server will not assert.

### Billing

| Event | Price |
|---|---|
| Server start (`apify-actor-start`) | $0.05, charged once per run by the platform |
| Tool call (`mcp-tool-call`) | $0.05 per completed tool call |

One flat charge per **completed** tool call. A DOI that Crossref returns 404 for is a sourced
answer ("not in Crossref") and **is** charged; a search matching zero works **is** charged. A
malformed DOI, an empty query, or an upstream Crossref failure is a notice and **is not**
charged.

### Source

The Crossref REST API, queried anonymously in the polite pool with a `mailto`. No API key.
`is-referenced-by-count` reflects Crossref's coverage (a lower bound), not a universal count.

# Actor input Schema

## `note` (type: `string`):

This Actor runs as an MCP server in Standby mode. Connect an MCP client to the server URL with path /mcp; there is no batch input to fill in.

## Actor input object example

```json
{
  "note": "standby"
}
```

# Actor output Schema

## `results` (type: `string`):

No description

# API

You can run this Actor programmatically using our API. Below are code examples in JavaScript, Python, and CLI, as well as the OpenAPI specification and MCP server setup.

## JavaScript example

```javascript
import { ApifyClient } from 'apify-client';

// Initialize the ApifyClient with your Apify API token
// Replace the '<YOUR_API_TOKEN>' with your token
const client = new ApifyClient({
    token: '<YOUR_API_TOKEN>',
});

// Prepare Actor input
const input = {
    "note": "standby"
};

// Run the Actor and wait for it to finish
const run = await client.actor("nexgenwatch/crossref-citation-mcp").call(input);

// Fetch and print Actor results from the run's dataset (if any)
console.log('Results from dataset');
console.log(`💾 Check your data here: https://console.apify.com/storage/datasets/${run.defaultDatasetId}`);
const { items } = await client.dataset(run.defaultDatasetId).listItems();
items.forEach((item) => {
    console.dir(item);
});

// 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/js/docs

```

## Python example

```python
from apify_client import ApifyClient

# Initialize the ApifyClient with your Apify API token
# Replace '<YOUR_API_TOKEN>' with your token.
client = ApifyClient("<YOUR_API_TOKEN>")

# Prepare the Actor input
run_input = { "note": "standby" }

# Run the Actor and wait for it to finish
run = client.actor("nexgenwatch/crossref-citation-mcp").call(run_input=run_input)

# Fetch and print Actor results from the run's dataset (if there are any)
print(f"💾 Check your data here: https://console.apify.com/storage/datasets/{run.default_dataset_id}")
for item in client.dataset(run.default_dataset_id).iterate_items():
    print(item)

# 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/python/docs/quick-start

```

## CLI example

```bash
echo '{
  "note": "standby"
}' |
apify call nexgenwatch/crossref-citation-mcp --silent --output-dataset

```

## MCP server setup

```json
{
    "mcpServers": {
        "apify": {
            "type": "http",
            "url": "https://mcp.apify.com/?tools=fetch-actor-details,nexgenwatch/crossref-citation-mcp"
        }
    }
}
```

The hosted server signs you in with OAuth on first connect, so no API token belongs in this config. Clients without OAuth support can send an `Authorization: Bearer <APIFY_API_TOKEN>` header instead, using a token from API & Integrations in Apify Console (https://console.apify.com/settings/integrations).

## OpenAPI specification

Download the OpenAPI definition: https://api.apify.com/v2/actors/U4icWBeWwvEJKaI2K/builds/5fk4IXXUmPN2t3V6r/openapi.json