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Metis Check

Official registry Other

Checks an answer's citations at the registries that issue them. Every check files a signed report.

Source code Website Documentation

Install

Add this to your client's MCP configuration (Claude Desktop: claude_desktop_config.json; Cursor: .cursor/mcp.json; VS Code and others use the same "mcpServers" shape).

Remote (streamable-http)
Claude Code 
claude mcp add --transport http metis-check 'https://check-api.metisfoundry.com/mcp/check'
JSON configuration (Claude Desktop, Cursor, VS Code) 
{
    "mcpServers": {
        "metis-check": {
            "type": "http",
            "url": "https://check-api.metisfoundry.com/mcp/check"
        }
    }
}

Documentation

From the project's README on GitHub, refreshed weekly. Links open on GitHub.

Contents
  1. Metis Check
  2. Install
  3. Try it in one click
  4. What you get
  5. Plans
  6. Repository layout
  7. Support and license

Metis Check

The check every cited AI answer needs before you rely on it. A citation that looks complete and points to nothing costs a correction, a retraction or a sanction. Metis Check asks the registries that issue each identifier whether it exists and what it says. DOI, PubMed, arXiv, ORCID, ROR, ISBN, LEI, ISIN, CUSIP, SEC CIK, EIN, NPI, UK company numbers, domains and more. Each identifier comes back in exactly one of four states: settled true, settled false, not decidable (a person decides) or unreachable (a delay, not evidence). Every check ends in a signed report with its own id, a PDF and a recheck button anyone can press.

By Metis Foundry. One account covers ChatGPT, Codex, Claude, Claude Code, Cursor and VS Code. Every account starts with 5 checks a month; plans.

A real report: three identifiers settled true, one settled false. Open it and press Recheck.

Install

ClientHow
Claude (web, desktop, mobile)Settings → Connectors → add a connector by URL: https://mcp.metisfoundry.com/mcp. Once Metis Check is listed in the connectors directory, choose it there.
Claude Code/plugin marketplace add MetisFoundry/metis-plugins then /plugin install metis-check@metis, or claude mcp add --transport http metis-check https://mcp.metisfoundry.com/mcp
Codex CLIcodex plugin marketplace add MetisFoundry/metis-plugins then codex plugin add metis-check@metis
ChatGPTThe Metis Check plugin is submitted to the OpenAI directory. Until it is listed: Settings → Connectors → add by address https://check-api.metisfoundry.com/mcp/check
CursorAdd to Cursor
VS CodeAdd to VS Code (web redirect), or code --add-mcp '{"name": "metis-check", "type": "http", "url": "https://check-api.metisfoundry.com/mcp/check"}'
Any MCP clientRemote server https://check-api.metisfoundry.com/mcp/check (OAuth sign-in; a free account is created on first connection). Registry name com.metisfoundry/metis-check.

Sign in or create a free Metis account when the client asks.

Try it in one click

The prompt asks Metis Check to check four references, one of them invented. The invented one comes back settled false, with the registry that said so.

What you get

  • Four states, nothing hidden: settled true, settled false, not decidable, unreachable, and a not-checked list with the reason for each.
  • A report that rechecks without Metis: every line carries the registry query and the SHA-256 of the registry's answer; signed JSON and a PDF.
  • Shareable: anyone with the link can open the report and press Recheck; the registries are asked again, live.
  • Private: passages are never stored, only the identifiers, their positions and a hash. Metis never asks for conversation history.
  • Honest scope: Metis Check establishes that an identifier is registered and what the registry says. It does not decide whether a paper supports a claim.

Plans

Free: 5 checks a month. Pro: $29 a month (or $276 a year), 2,000 checks, case law included. Team: $249 a month (or $2,388 a year), 15,000 checks, 5 seats. Checks that cannot be settled cost nothing. Details: https://check-api.metisfoundry.com/check/plans

Repository layout

  • .agents/plugins/marketplace.json — Codex marketplace (metis); plugin in plugins/metis-check
  • .claude-plugin/marketplace.json — Claude Code marketplace (metis); plugin manifest in plugins/metis-check/.claude-plugin
  • server.json — official MCP Registry manifest
  • PUBLISH.md — how the listings are published

Support and license

hello@metisfoundry.com. The files in this repository are MIT licensed (LICENSE); the Metis Check service is proprietary (NOTICE.md).

Frequently asked questions

What is Metis Check?

Checks an answer's citations at the registries that issue them. Every check files a signed report.

How do I install Metis Check?

It runs as a remote server. In Claude Code: claude mcp add --transport http metis-check 'https://check-api.metisfoundry.com/mcp/check'. For other clients, paste the JSON configuration from this page into their MCP settings.

Does Metis Check need an API key?

Its registry entry lists no required key or secret. Some features may still need an account with the service it connects to.

Is Metis Check open source?

Its code is public on GitHub, but the repository does not declare a standard license.

Who maintains Metis Check?

It is published by MetisFoundry. AI.tn lists it but does not maintain or endorse it.

From the official MCP Registry. Listing is not an endorsement: review a server's code and permissions before giving it access to your data.