Citation Check

Checks every reference in a paper, brief or bibliography before anyone relies on it: does the cited work exist, does the citation describe it correctly, and has it been retracted?

Language models fabricate references, and fabricated references now reach court filings and journal submissions (Damien Charlotin's database of AI-hallucination cases in courts lists more than two thousand decisions). The existing checkers either stop at "is this DOI valid" or miss retractions. Citation Check gives each reference a verdict an agent can act on:

Every result also carries flags such as retracted, partially_retracted, expression_of_concern, corrected, doi_added, identifier_points_to_different_work, doi_not_registered, published_version_exists and doi_may_be_later_copy, with the notice DOIs and dates. The last one catches a quiet index error: OpenAlex sometimes files a classic paper under the DOI of a later repost or book chapter, which shows because the work is cited years before that DOI's date.

It reads pasted reference lists in any common style (Vancouver, APA, numbered, one per line) and BibTeX, and returns corrected BibTeX that keeps your citation keys. No account or key needed.

Built and maintained by Arhan Canli.

Install

Needs Node.js 20 or newer. No account or key.

Claude Code

claude mcp add citation-check -- npx -y citation-check-mcp

Claude Desktop: download citation-check-mcp-<version>.mcpb from the latest release and open it. The bundle is signed; verify it with gh attestation verify <file> --repo arhancanli/citation-check-mcp.

Any other client (Windsurf, Zed, Cline, Continue and others), in its MCP config file:

{
  "mcpServers": {
    "citation-check": {
      "command": "npx",
      "args": [
        "-y",
        "citation-check-mcp"
      ]
    }
  }
}

Docker

docker build -t citation-check-mcp https://github.com/arhancanli/citation-check-mcp.git && docker run -i --rm citation-check-mcp

Hosted (Streamable HTTP): node src/server.mjs --http serves stateless MCP at POST /mcp (port from PORT, default 3000).

Optional settings

• CROSSREF_MAILTO: your own email address. Crossref then serves requests from its faster "polite" pool (3 searches per second instead of 1). Nothing else is done with it.

• OPENALEX_API_KEY: a free OpenAlex key raises its daily search allowance. Without one, OpenAlex is used only as the last fallback and the check still completes when its allowance is spent.

Related MCP server: io.github.Hylouis233/bibverify

Example

An agent calls check_references with:

{
  "text": "1. Wakefield AJ, Murch SH, Anthony A, et al. Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. Lancet. 1998;351(9103):637-641.\n2. Kucsko G, Maurer PC, Yao NY, et al. Nanometre-scale thermometry in a living cell. Nature. 2013;500:54-58. doi:10.1038/nature12373\n3. Vaswani A, Shazeer N, Parmar N, et al. Attention is all you need. In: Advances in Neural Information Processing Systems. 2017.\n4. Smith J, Doe R. Quantum entanglement improves photosynthesis yields in wheat. Nature Plants. 2021;7:112-119. doi:10.1038/nature12373\n5. Kucsko G, Maurer PC. Nanometre-scale thermometry in a living cell. Nature. 2011;500:54-58.\n6. Chen L, Okafor B. Neural cartography of hallucinated citations in legal briefs. Journal of Imaginary Studies. 2022;14(2):33-47."
}

and gets back (recorded from the live server on 2026-09-27):

{
  "counts": {
    "verified": 3,
    "mismatch": 2,
    "not_found": 1,
    "unverifiable": 0,
    "retracted": 1
  },
  "results": [
    {
      "n": 1,
      "cited": "Wakefield AJ, Murch SH, Anthony A, et al. Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. Lancet....",
      "verdict": "verified",
      "flags": [
        "doi_added",
        "corrected",
        "retracted"
      ],
      "matched": {
        "doi": "10.1016/s0140-6736(97)11096-0",
        "title": "RETRACTED: Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children",
        "authors": "Wakefield, Murch, Anthony et al.",
        "year": 1998,
        "venue": "The Lancet",
        "url": "https://doi.org/10.1016/s0140-6736(97)11096-0",
        "source": "crossref"
      },
      "notices": [
        {
          "type": "correction",
          "notice_doi": "10.1016/s0140-6736(04)15715-2",
          "date": "2004-03-06"
        },
        {
          "type": "retraction",
          "notice_doi": "10.1016/s0140-6736(10)60175-4",
          "date": "2010-02-06"
        }
      ]
    },
    {
      "n": 2,
      "cited": "Kucsko G, Maurer PC, Yao NY, et al. Nanometre-scale thermometry in a living cell. Nature. 2013;500:54-58. doi:10.1038/nature12373",
      "verdict": "verified",
      "matched": {
        "doi": "10.1038/nature12373",
        "title": "Nanometre-scale thermometry in a living cell",
        "authors": "Kucsko, Maurer, Yao et al.",
        "year": 2013,
        "venue": "Nature",
        "url": "https://doi.org/10.1038/nature12373",
        "source": "crossref"
      }
    },
    {
      "n": 3,
      "cited": "Vaswani A, Shazeer N, Parmar N, et al. Attention is all you need. In: Advances in Neural Information Processing Systems. 2017.",
      "verdict": "verified",
      "flags": [
        "doi_added"
... (60 more lines)

Tools

How it works

1. Identifiers first, in batches: DOIs through Crossref (40 per request), arXiv ids through DataCite, PMIDs through PubMed, and any DOI that neither Crossref nor DataCite knows through doi.org, which says whether any registration agency has it at all.

2. Citations without an identifier, or whose DOI points at a different work, are searched in Crossref, then by title (and first author) in DataCite, which holds arXiv, then in OpenAlex.

3. The best candidate is chosen by comparing title, first author and year, never by a source's own ranking alone: Crossref ranks a same-titled letter above the original paper for some queries, and both Crossref and OpenAlex rank reposts of famous papers above the original.

4. Retractions, corrections and expressions of concern come from Crossref, which includes the Retraction Watch database.

How it behaves

• Read-only: no tool changes anything outside this process.

• Network: HTTPS only, to the hosts listed in package.json under factory.allowHosts, with a deadline, a size cap and bounded retries. Nothing else is contacted, and nothing is logged except unexpected failures (to stderr, without your inputs).

• Keeps to each source's published limits (Crossref: 5 lookups and 1 search per second, one at a time, or its polite-pool limits with CROSSREF_MAILTO; NCBI: 3 per second), and caches answers for 30 minutes.

• Up to 30 references per check_references call. A reference with a DOI costs a fraction of one without, so free-text lists take about a second per reference on Crossref's public pool.

• Results are compact JSON with a matching output schema.

Benchmark

Measured 2026-09-26 with gpt-5.4-mini, 10 fixed tasks graded by fixed checks (bench/tasks.json, raw results in bench/results/).

Performance

Measured 2026-09-27 from Dubai, home connection against the live upstream, Node 24.19.0 (bench/perf.json, scripts/perf.mjs in the factory).

First call: a fresh server process, including the TLS connection and the upstream's own time. Repeat: the same call again, answered from the in-process cache, so it shows this server's own overhead.

Tool definitions the model reads on every turn (name, description, input schema): 1,523 characters, against 2,550 for doi-mcp, the most starred citation verifier. The full tool list, with the output schemas and annotations clients use to validate results, is 2,979 characters (2,913 for the alternative).

Data sources

• Crossref REST API: bibliographic metadata and update notices, including the Retraction Watch database that Crossref makes openly available.

• DataCite REST API: arXiv and other DataCite DOIs.

• PubMed through NCBI E-utilities.

• OpenAlex: search fallback (CC0 data).

• doi.org handle API: whether a DOI is registered at all.

More MCP servers by Arhan Canli

• Actions Check: Checks GitHub Actions workflows: outdated actions, old Node runtimes, retired runners, injection.

• Config Check: Validates config files against their official schemas: tsconfig, compose, workflows, 1,400+ more.

• Contact Check: Validates and formats phone numbers, email addresses and postal addresses for any country.

• Cron Check: Explains cron expressions, lists next run times in any time zone, converts between cron dialects.

• Dockerfile Check: Checks Dockerfiles: build-breaking mistakes, base image tags that exist, digests, platforms, EOL.

• Domain Health: Email and domain checks: SPF lookup limits, DKIM keys, DMARC, DNS records, registration expiry.

• Drug Label: FDA drug label answers with section citations, RxNorm name resolution, recalls and shortages.

• End of Life: Is this version still supported? EOL dates, latest patch and upgrade target for 470+ products.

• The whole collection, 12 more

License

MIT, Copyright (c) 2026 Arhan Canli.