VerifyAPI — fact-check with signed receipts MCP server

VerifyAPI MCP Server

Fact-check any claim before you act on it. One tool. Live web sources. Cryptographically signed receipts.

What it does: VerifyAPI is a Model Context Protocol server that verifies factual claims against live web sources and returns a citable verdict — including the source URL, published date, a verbatim quote, and an Ed25519-signed receipt so downstream systems can prove the check actually happened.

When to use it: Any time your agent is about to act on a factual claim it can't cite. Prices, dates, versions, quotes, statistics, product specs, event outcomes. If getting it wrong would cost time, money, or trust — verify first.

Quick install (Claude Desktop / Cursor / Cline / any MCP client)

{
  "mcpServers": {
    "verifyapi": {
      "command": "npx",
      "args": ["-y", "@verify-api/mcp@latest"],
      "env": {
        "VERIFYAPI_API_KEY": "csk_live_..."
      }
    }
  }
}

No API key? Leave VERIFYAPIAPIKEY unset for the free trial (limited to 3 calls per IP per 24h, signed receipts included). Get a free key at https://verify-api.dev/signup — no credit card required.

The one tool: verify_claim

Input:

{
  "claim": "Python 3.13 was released in October 2024."
}

Output:

{
  "verdict": "supported",
  "confidence": 0.99,
  "source_url": "https://docs.python.org/3/whatsnew/3.13.html",
  "exact_quote": "Python 3.13 was released on October 7, 2024.",
  "reasoning": "Multiple authoritative sources confirm...",
  "receipt": {
    "jws": "eyJhbGci...",
    "kid": "pQAd73zRp9Xq9Y5U"
  }
}

Verdicts: supported, contradicted, unverifiable. Every supported/contradicted verdict comes with a JWS receipt signed by keys served at https://api.verify-api.dev/.well-known/jwks.json.

Why signed receipts?

Because "the AI checked" is not the same as "the AI verified." A signed receipt lets a downstream system — compliance auditor, user, another agent, a smart contract — cryptographically prove that a specific claim was verified against a specific source at a specific time by VerifyAPI's known public key. It's the difference between saying "trust me" and handing over a notarized document.

Pricing

• Free trial: no signup, no card. Limited to 3 calls per IP per 24h. Includes signed receipts.
• With API key: $0.02 per verified claim. Unverifiable / out-of-scope calls are free (you don't pay for "I couldn't find enough evidence").
• Freshness tiers: standard verification $0.02, real-time (fresh-fetch) $0.05.
• Auto top-up: save a card, set a threshold, keep flowing. POST /v1/balance/autorefill.

Example use cases

LangChain / LlamaIndex agents: wrap verify_claim as a Tool. Have your agent call it before returning any factual answer.

Cursor / Cline coding agents: verify version numbers, API existence, deprecation status before writing imports.

Claude Desktop workflows: "Verify this quote is real before I put it in the deck."

Multi-agent systems: pass receipts between agents to prove groundedness up the chain.

Compliance-sensitive automation: keep the JWS receipts as audit trail for every factual decision the agent made.

Environment variables

Programmatic API (skip MCP, call directly)

curl -X POST https://api.verify-api.dev/v1/verify \
  -H "Authorization: Bearer csk_live_..." \
  -H "Content-Type: application/json" \
  -d '{"claim": "Bitcoin ETFs were approved by the SEC in January 2024."}'

Full OpenAPI spec: https://api.verify-api.dev/openapi.json

Shortened. The full README is on GitHub.