io.github.JonasFuchss/x402-trust-mcp

x402-trust-mcp

An MCP server for discovering x402 endpoints and checking their trust before paying them: semantic and keyword search across the monitored catalog, plus trust scores, history, bulk scoring, and watches for any endpoint.

Backed by x402-trust.com, which monitors the x402 ecosystem on Base and Solana 24/7: uptime probes, 402-envelope spec compliance, price history, and real on-chain USDC settlement volume per endpoint. Every score is computed deterministically, no LLM involved, so the breakdown is fully auditable.

Tools

Paid tools cost from $0.005 (single lookup) to ~$0.50 (500-endpoint bulk), charged over x402 (USDC on Base). With X402_PRIVATE_KEY set the server auto-pays within your limits; otherwise it returns the price quote for your host to pay. List tools page with limit (max 25) + offset and return a total.

Field-level documentation, verdict semantics, watch cursor rules and webhook signature details live at x402-trust.com/llms.txt; every response is self-describing via its schema at x402-trust.com/schemas.

Install

Add to your MCP client config (e.g. Claude Desktop claude_desktop_config.json):

{
  "mcpServers": {
    "x402-trust": {
      "command": "npx",
      "args": ["-y", "x402-trust-mcp"]
    }
  }
}

To enable autonomous payment for the paid tools, add a funded Base USDC wallet:

{
  "mcpServers": {
    "x402-trust": {
      "command": "npx",
      "args": ["-y", "x402-trust-mcp"],
      "env": {
        "X402_PRIVATE_KEY": "0xYOUR_BASE_WALLET_KEY",
        "X402_MAX_USD": "0.05"
      }
    }
  }
}

Configuration (env vars)

The free tools work with no configuration at all.

Security

X402_PRIVATE_KEY is a hot wallet: fund it with only what you are willing to spend on trust lookups. The key never leaves your machine; it signs EIP-3009 payment authorizations locally, after policy checks: chain allow-list (Base mainnet by default), canonical USDC contract verification, and the spend and call-count caps above. Before every payment the client re-reads the wallet's USDC balance: a wallet that cannot cover the quote is refused locally, before anything is signed, so an empty wallet never produces failed settlement attempts, and a top-up takes effect on the very next call.

Response signatures

Signed tool results carry a top-level signature block: an Ed25519 signature over the JCS-canonicalized (RFC 8785) response. It proves the content was assembled by x402-trust and not modified afterwards.

One rule matters when verifying: pin the trust anchor, never follow it from the response. signature.publicKeys is a discovery hint; a forged response would point at the attacker's own key document and still verify. Pin the public key itself or fetch https://x402-trust.com/.well-known/x402-trust-keys.json once at bootstrap and cache it. A worked test vector and a 20-line reference verifier live at x402-trust.com/schemas. Watch management responses are unsigned by design: they carry capability secrets that must never be forwarded as evidence.

License

MIT