citeguard-mcp-server

An MCP server that checks a citation against Crossref for retraction, correction, or expression-of-concern status — so an AI agent doing research, writing, or literature review can check its own citations before including them. No API key required; Crossref's REST API is free and open.

Part of the citeguard project — see the repository root for the shared detection logic and the Python CLI/library. This server is an independent TypeScript implementation of the same, empirically-verified detection algorithm, tested against the same real Crossref fixtures as the Python package (tests/fixtures/) so both surfaces agree on ground truth.

Tools

• check_citation — check a single DOI.
• check_citations — extract every DOI from a block of text (a reference list, a paper draft) and check them all in one call.

Install and configure

Nothing to clone or build — add this to your MCP client's config (e.g. claude_desktop_config.json, or a project's .mcp.json for Claude Code):

{
  "mcpServers": {
    "citeguard": {
      "command": "npx",
      "args": ["-y", "citeguard-mcp-server"]
    }
  }
}

git clone https://github.com/wedo911/citeguard.git
cd citeguard/mcp-server
npm install
npm run build

{
  "mcpServers": {
    "citeguard": {
      "command": "node",
      "args": ["/absolute/path/to/citeguard/mcp-server/dist/index.js"]
    }
  }
}

Troubleshooting: network errors for every DOI

If check_citation fails on every DOI (not just retracted or unusual ones) with a network/fetch error, this is very likely an environment issue, not a bug: many MCP clients spawn servers with a minimal, security-conscious environment — the official SDK's default, for example, only passes through HOME, LOGNAME, PATH, SHELL, TERM, and USER, not your full shell environment. If your network requires something outside that list to make outbound HTTPS calls — NODE_EXTRA_CA_CERTS (common with corporate proxies or antivirus TLS inspection, e.g. Norton), HTTP_PROXY/HTTPS_PROXY, or similar — the spawned server won't have it and every HTTPS request will fail with a generic error.

This is exactly what happened during this project's own development and testing: this server's Crossref client was independently verified correct via direct execution, then failed with fetch failed the moment it was spawned as a child process by an MCP client using default environment inheritance — resolved once NODE_EXTRA_CA_CERTS was included in the spawned environment. If you hit this, configure your MCP client to pass through the specific variable your network needs (check your client's documentation for an env field in its server configuration).

Run the tests

npm run build
node --test tests/analyze.test.mjs tests/parsers.test.mjs

Try it without a client

npx @modelcontextprotocol/inspector --cli node dist/index.js \
  --method tools/call --tool-name check_citation \
  --tool-arg doi="10.1016/S0140-6736(97)11096-0"

License

MIT — see LICENSE in the repository root.