code402

npx add-mcp 'https://hcrb.in/mcp'

@code402/verify-mcp

Verify code402 XDR-1 receipts from any MCP client. Every result a code402 endpoint returns carries a signed receipt; this server checks the signature deterministically — keccak-256 over the canonical receipt, secp256k1 public-key recovery, compared to the declared signer. Free, stateless, no account: the verifier holds no keys and performs no settlement.

Use with Claude Desktop / Cursor

{
  "mcpServers": {
    "code402-verify": {
      "command": "npx",
      "args": ["-y", "@code402/verify-mcp@latest"]
    }
  }
}

Tool

x402_verify — verify one receipt:

{ "raw_receipt": "<the full signed receipt JSON as a string>" }

Result:

{
  "valid": true,
  "payer": "0x…",
  "amount": "5000",
  "receipt_hash": "0x…",
  "_meta": {
    "verified_by": "code402",
    "network": "base-mainnet",
    "signer": "0xa036…",
    "signer_recovered": "0xa036…",
    "attestation_url": "https://hcrb.in/audit/0x…"
  }
}

How it works

Local-first (since 0.2.0): verification runs entirely on your machine — keccak-256 over the canonical receipt, secp256k1 public-key recovery, compared to the declared signer. No network calls, no keys held, nothing to trust but the math. Set CODE402_VERIFY_URL to proxy to the hosted verifier at verify.code402.dev instead — verdicts are identical by construction (deterministic recomputation over public data).

Stdout carries only clean single-line JSON-RPC 2.0 frames; every diagnostic goes to stderr (a hard requirement for Docker and desktop MCP runners).

Verification is pure recomputation over public data — the same operation any agent can run offline against its own receipts.

The hosted verifier's exact source (public)

worker/ in this repo is the complete source of the hosted verifier at verify.code402.dev (a dedicated Cloudflare worker, extracted from the rail monolith 2026-09-23: 3ms startup vs the monolith's measured 11.3s cold start). Same canon + keccak-256 + secp256k1 recovery, byte-identical verdicts — pinned by worker/test/index.spec.ts against a real minted receipt. The public can audit exactly what verifies their receipts.

License

MIT