Metis Check

Checks the citations in an answer at the registries that issue them (DOI, PubMed, arXiv, LEI, ORCID, ROR, ISBN, SEC CIK and more) and files a signed report anyone can recheck. Each identifier comes back in one of four states: settled true, settled false, not decidable, unreachable. Works inside ChatGPT, Codex, Claude and Claude Code. Free: 5 checks a month.

View on metisfoundry.com

Hosted MCP Server

npx add-mcp 'https://check-api.metisfoundry.com/mcp/check'

Installs into Claude Code, Codex, Cursor and more

Documentation

Bring source checks into Claude.

  1. Create a free Metis account, or use your existing Metis client username.
  2. In Claude, open Settings → Connectors and choose Metis Check. If it is not listed for you yet, add it by address: https://mcp.metisfoundry.com/mcp, named Metis Check.
  3. Sign in with your Metis customer account and approve the verification permission.
  4. Ask: “Use Metis to check DOI 10.1038/nphys1170.”

Automatic citation checks, with an off switch

In Claude, say “Turn on Metis auto-check for citations in this conversation.” Claude can use the auto-check tool for supported identifiers as it answers. Say “Turn off Metis auto-check” at any time, or disable the connector in Claude. Turning it off prevents subsequent automatic checks; a check already running may finish.

Metis stops automatic checks at your monthly allowance and never starts an overage payment. You can ask “How many Metis checks do I have left?” Auto-check starts off. It depends on Claude calling the tool; Metis cannot watch conversations in the background or verify every factual claim.

Verified by a person

On the Verified plan, say “Ask a Metis researcher to verify Metis Check report MC-…” and a person verifies the identifiers in that report in real time while you work; the result is filed on the same report as a signed addendum with the reviewer’s name and the date. Say “Turn on Metis live verification” and a researcher verifies every report this account files for the next eight hours; the findings appear in later answers and on each report. A researcher confirms that each identifier resolves to the work or entity the citation names, and what the registry and the source document say; not whether the surrounding argument is true. Human verification is included in the Verified plan; see the Metis Check plans page.

What the connector receives

Only the identifiers submitted to the tool. Do not send a whole conversation. Claude receives the returned registry evidence and any available receipt and transparency-log information.

Current release

Every account starts with 5 checks a month. The plan, the monthly allowance and the reports are shared with Metis Check in ChatGPT and Codex: one account, one meter, one subscription. See your Metis Check plan.

One check means one identifier settled true or false at its registry; a registry that cannot decide or cannot be reached costs nothing. U.S. case citations are checked against the CourtListener index (a citation index, not the court) on Pro, Team and Verified.

Open the public Metis checker