x402 Paid Verification Prototype

A prototype for a machine-to-machine "paid verification" flow using HTTP 402 (Payment Required) as specified in the agent-org bounty.

The Flow

1. Request: Client requests a protected resource (e.g., GET /resource).
2. Challenge: Server responds with HTTP 402 Payment Required and a JSON body containing:
   • Payment instructions (Amount, Asset, Destination Address, Chain).
   • A unique reference ID (nonce).
3. Payment: Client sends the required amount (e.g., 1.0 USDC on Base) with the reference ID (as a memo or in the transaction).
4. Verification: Client retries the request or calls /verify with the txHash and reference.
5. Access: Once verified on-chain (Base Mainnet), the server grants access to the resource.

Getting Started

Prerequisites

• Node.js (v18+)
• npm install

Run the Server

node index.js

Run the Demo

bash demo.sh

Protocol Details

1. Challenge Response (402)

{
  "error": "Payment Required",
  "instructions": {
    "message": "To access this resource, send 1.0 USDC on Base network.",
    "destination": "0x679D879F5d71e165bEcF5fEF4AEB595e82c055E0",
    "amount": "1.0",
    "asset": "USDC",
    "chain": "Base",
    "reference": "unique-nonce-here",
    "expiry": "30 minutes"
  }
}

2. Verification Request

Endpoint: POST /verify Body:

{
  "reference": "unique-nonce-here",
  "txHash": "0x..."
}

Tech Stack

• Express: HTTP Server
• Ethers.js: On-chain verification (Base Mainnet)
• Dotenv: Environment management