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VerifyAPI — fact-check with signed receipts

Official registry Security

Fact-check any claim with live web sources. Ed25519-signed receipts. Catches hallucinations.

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).

NPM package @verify-api/mcp
Claude Code 
claude mcp add verifyapi-fact-check-with-signed-receipt -e 'VERIFYAPI_API_KEY=<your verifyapi_api_key>' -e 'VERIFYAPI_BASE_URL=<VERIFYAPI_BASE_URL>' -- npx -y @verify-api/mcp@0.1.9
JSON configuration (Claude Desktop, Cursor, VS Code) 
{
    "mcpServers": {
        "verifyapi-fact-check-with-signed-receipt": {
            "command": "npx",
            "args": [
                "-y",
                "@verify-api/mcp@0.1.9"
            ],
            "env": {
                "VERIFYAPI_API_KEY": "<your verifyapi_api_key>",
                "VERIFYAPI_BASE_URL": "<VERIFYAPI_BASE_URL>"
            }
        }
    }
}

Environment variables

  • VERIFYAPI_API_KEY secret Your VerifyAPI key (csk_live_...). Get one free at https://verify-api.dev/signup — no card required. Unset = free trial (3 calls per IP per 24h, cached tier, signed receipts still included).
  • VERIFYAPI_BASE_URL Override the API base URL. Defaults to https://api.verify-api.dev.

Documentation

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

Contents
  1. VerifyAPI MCP Server
  2. Quick install (Claude Desktop / Cursor / Cline / any MCP client)
  3. The one tool: verify_claim
  4. Why signed receipts?
  5. Pricing
  6. Example use cases
  7. Environment variables
  8. Programmatic API (skip MCP, call directly)
  9. Links
  10. Built by
  11. License

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 VERIFYAPI_API_KEY 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

VariableRequiredDefaultDescription
VERIFYAPI_API_KEYNo(unset = trial)Your VerifyAPI key (csk_live_...). Get one free at https://verify-api.dev/signup
VERIFYAPI_BASE_URLNohttps://api.verify-api.devOverride the API base URL. Useful for self-hosting or testing.

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

x402 payment support built in — see https://verify-api.dev/agents.txt for the agent-native discovery manifest.

Built by

Circuit Savers LLC — Wausau, Wisconsin.

License

MIT

Frequently asked questions

What is VerifyAPI — fact-check with signed receipts?

Fact-check any claim with live web sources. Ed25519-signed receipts. Catches hallucinations.

How do I install VerifyAPI — fact-check with signed receipts?

It runs on your machine. In Claude Code: claude mcp add verifyapi-fact-check-with-signed-receipt -e 'VERIFYAPI_API_KEY=<your verifyapi_api_key>' -e 'VERIFYAPI_BASE_URL=<VERIFYAPI_BASE_URL>' -- npx -y @verify-api/mcp@0.1.9. For other clients, paste the JSON configuration from this page into their MCP settings.

Does VerifyAPI — fact-check with signed receipts need an API key?

Yes. It expects VERIFYAPI_API_KEY, which you set in its configuration.

Is VerifyAPI — fact-check with signed receipts open source?

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

Who maintains VerifyAPI — fact-check with signed receipts?

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

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