x402 Notary MCP server

x402 Notary — Cryptographic Receipts for AI Outputs

A ForgeMesh Labs product — the notary of the x402 agent economy.

Prove what your AI said, when it said it, and which model said it.

Every AI output is just text. There's no proof a specific model produced a specific response at a specific time — and as agents start hiring other agents, that trust gap gets expensive. x402 Notary closes it: submit any inference, pay $0.001 in USDC (automatic, via x402 on Base or Solana — no API key, no account), and get back a signed, timestamped, chain-anchored receipt that anyone can verify, free, forever.

We notarize the hash, not your secrets. Your prompt and response are hashed and signed — never stored. Private signed receipts, publicly anchored by batch root.

Quick start: Base (Claude Desktop / Claude Code / any MCP client)

{
  "mcpServers": {
    "x402-notary": {
      "command": "npx",
      "args": ["-y", "@forgemeshlabs/x402-notary-mcp"],
      "env": {
        "WALLET_PRIVATE_KEY": "0x..."
      }
    }
  }
}

WALLETPRIVATEKEY is a dedicated low-balance Base wallet for x402 micropayments — never your primary wallet. $1 of USDC notarizes 1,000 outputs.

Quick start: Solana

{
  "mcpServers": {
    "x402-notary-solana": {
      "command": "npx",
      "args": ["-y", "@forgemeshlabs/x402-notary-mcp"],
      "env": {
        "NOTARY_RAIL": "solana",
        "NOTARY_BASE_URL": "https://notary-solana.forgemesh.io",
        "SOLANA_PRIVATE_KEY": "[1,2,...]"
      }
    }
  }
}

SOLANAPRIVATEKEY is a dedicated low-balance Solana keypair for x402 micropayments. It may be a JSON byte array, base58, base64, or hex-encoded 32/64-byte key. Never use your primary wallet.

Verification needs no wallet at all. Skip the env block entirely and you can still verify receipts, inspect attestations, and read live stats.

Tools

What a receipt proves

When you notarize an inference you get an attestation:

{
  "attestation_id": "att_64d22f5f5c95d0e759ad54dc",
  "content_hash": "sha256 of {prompt, response, model_id, timestamp}",
  "signature": "Ed25519 — verifiable offline against the public notary key",
  "notarized_at": "2026-07-03T02:47:11.000Z",
  "anchor": { "status": "sealed", "merkle_root": "…", "proof": ["…"] }
}

That's proof of three things:

1. Existence — this exact content existed at this exact time.
2. Integrity — change one character of the prompt or response and verification fails.
3. Independence — signatures verify offline with the published key; Merkle roots anchor batches. You don't have to trust the notary's word after the fact.

Verify anything, free, from anywhere

Any agent (or human, or CI job) can check a receipt before acting on the output behind it:

Shortened. The full README is on GitHub.