Verify API MCP Server

MCP server for Verify API: a pay-per-call verification service that gives agents a fast, structured, evidence-backed yes/no/unknown on claims they'd otherwise guess at.

Stop your agent from citing things that don't exist, installing things that shouldn't, or paying sellers that don't check out. Six tools, one answer each, evidence attached.

Tools

• verify_citation -- does a citation exist, is it retracted, and does the given title/authors/year/journal match the canonical record? Checked against Crossref (includes Retraction Watch data) with OpenAlex as a fallback.
• verify_url -- does a URL resolve, what's the final status and redirect chain, is it archived on the Wayback Machine, and (optionally) does expected text appear on the page?
• verify_package -- does an npm/PyPI/crates.io package exist, is it deprecated or yanked, and does it have known vulnerabilities? Checked against the registry plus OSV.dev advisories. Catches an agent installing a hallucinated or squatted package name.
• verify_repo -- does a GitHub repo exist, is it archived or disabled? Checked against the GitHub REST API. Catches an agent recommending or depending on a renamed, taken-down, or abandoned repo.
• verify_case -- does a legal case citation exist, and does the given case name match the canonical record? Checked against CourtListener. Catches a fabricated case citation, including a real-looking citation number paired with an invented case name. Existence only -- does not check whether a case is still good law.
• verify_seller -- before paying an x402 seller, does it exist and respond with a well-formed 402 challenge, is its own declared input/output schema internally consistent, and is its payout address sanctioned? Checked live against the seller itself plus a sanctions oracle and on-chain wallet history (Base payTo addresses only). Confirms the checkable things check out -- not a guarantee of trustworthiness.

Every response includes a verdict (confirmed / contradicted / unknown), the individual checks that were run, and evidence with source URLs so a human can verify the answer themselves. unknown is a valid, honest answer -- this server never guesses to avoid it.

Install

pip install verify-api-mcp

Configure

The primary way to use Verify API is x402 pay-per-call (no key, no account, from $0.005/call -- $0.01 for verify_case) -- but this MCP server specifically needs a subscription key instead, since x402 requires a wallet most MCP clients don't have. Get one by subscribing to a plan at goodsong.dev/#pricing (Solo, $15/mo, or Team, $49/mo) -- the key is issued immediately on the checkout success page. There's no free tier.

Then add your key to your MCP client's config (e.g. mcp.json):

{
  "mcpServers": {
    "verify-api": {
      "command": "verify-api-mcp",
      "env": {
        "VERIFY_API_KEY": "vk_..."
      }
    }
  }
}

VERIFY_API_URL defaults to https://goodsong.dev and only needs to be set if you're pointing at a different deployment.

License

MIT