x402 Paywall Skill for OpenClaw

🚀 Reproduce in 3 Minutes

git clone https://github.com/BAiSEDagent/x402-paywall-skill.git
cd x402-paywall-skill
npm install
npm test

# Terminal 1 — start the demo server
npm run demo:server

# Terminal 2 — run the client
npm run demo:client

Or run the full flow in one command:

npm run buy-demo

x402 Paywall Skill for OpenClaw

OpenClaw USDC Hackathon — Best Skill Track

Enable autonomous agent-to-agent commerce using an x402-inspired protocol — HTTP 402 Payment Required responses with onchain USDC micropayments on Base L2.

Note on x402 compatibility: This implementation uses a "pay onchain → send txHash proof → verify on-chain" flow rather than EIP-712 signatures with atomic facilitator settlement as specified in the full x402 spec. The payment lifecycle (402 → pay → verify → serve) follows x402 semantics, with onchain verification through a deployed facilitator contract.

What This Skill Does

The x402 Paywall Skill enables OpenClaw agents to:

• Monetize premium content — Serve paid content using HTTP 402 responses
• Pay for services autonomously — Clients automatically handle payment flows
• Execute USDC micropayments — Real onchain transactions on Base
• Verify payments cryptographically — Trustless verification via smart contracts
• Enable agent commerce — True agent-to-agent economic interactions without human intervention

Architecture

Agent A (Client)           Agent B (Server)           Base Sepolia
     │                          │                          │
     │── GET /premium ─────────>│                          │
     │<── 402 + Payment Info ───│                          │
     │                          │                          │
     │── Approve USDC ────────────────────────────────────>│
     │── Submit Payment ──────────────────────────────────>│ PaymentFacilitator
     │                          │                          │
     │── GET /premium ─────────>│                          │
     │   + Payment Proof        │── Verify Payment ───────>│
     │                          │<── Valid ────────────────│
     │<── 200 + Content ────────│                          │

Payment Flow (Mermaid)

sequenceDiagram
    participant A as Agent A (Client)
    participant S as Agent B (Server)
    participant F as Facilitator Contract
    participant U as USDC Contract

    A->>S: GET /premium/analysis
    S->>A: 402 Payment Required + Payment Info
    A->>U: Approve USDC spending
    A->>F: submitPayment(id, payee, amount)
    F->>U: transferFrom(payer, facilitator, amount)
    A->>S: GET /premium/analysis + Payment Proof
    S->>F: verifyPayment(id, payer, amount)
    F->>S: true
    S->>A: 200 OK + Premium Content

Why Agent Commerce Matters

Technical Implementation

Smart Contract: PaymentFacilitator

Deployed on Base Sepolia. Handles the full lifecycle:

1. submitPayment(paymentId, payee, amount) — Payer deposits USDC, indexed by payment ID
2. verifyPayment(paymentId, payer, amount) — Server verifies payment exists and is valid
3. settlePayment(paymentId) — Payee marks payment as settled
4. withdraw() — Payee withdraws accumulated balance

Source: contracts/PaymentFacilitator.sol

Client Library: X402Client

Handles the full payment flow transparently:

const { X402Client } = require('./src/x402-client');

const client = new X402Client({
  wallet: myWallet,
  facilitatorAddress: '0x...'
});

// Automatically handles 402 → pay → retry
const response = await client.request('https://agent-b.com/premium/analysis');

Server Library: X402Server

Turn any content into a paid endpoint:

const { X402Server } = require('./src/x402-client');

const server = new X402Server({
  facilitatorAddress: '0x...',
  payeeAddress: myWallet.address
});

server.addContent('/analysis/defi', generateDeFiReport, 5.0); // 5 USDC

Base Sepolia Integration

• USDC Contract: 0x036CbD53842c5426634e7929541eC2318f3dCF7e
• Network: Base Sepolia (Chain ID: 84532)
• RPC: https://sepolia.base.org
• Explorer: https://sepolia.basescan.org

Quick Start

Installation

git clone https://github.com/BAiSEDagent/x402-paywall-skill.git
cd x402-paywall-skill
npm install

Run Tests

npm test

Run Demo

Start the paywall server (serves premium content behind 402):

npm run demo:server

In another terminal, run the client (requests content, sees 402 response):

npm run demo:client

Deploy Contract (Base Sepolia)

# Check wallet balance
node scripts/deploy.js balance

# Deploy facilitator + run demo payment
node scripts/deploy.js all

# Deploy contract only
node scripts/deploy.js deploy

# Run demo payment against existing deployment
node scripts/deploy.js pay

Proof of Work

Live on Base Sepolia — all transactions verifiable on-chain:

• Facilitator Contract: 0x28a1217aB0919ABc071EA101108d8ad4BbE7913e
• USDC Token: 0x036CbD53842c5426634e7929541eC2318f3dCF7e

Full details: scripts/proof-of-work.json

Testnet faucets (if deploying yourself):
- ETH: https://www.alchemy.com/faucets/base-sepolia
- USDC: https://faucet.circle.com (select Base Sepolia)

Project Structure

x402-paywall-skill/
├── SKILL.md                    # OpenClaw skill definition
├── README.md                   # This file
├── package.json
├── contracts/
│   └── PaymentFacilitator.sol  # Solidity contract (compiled)
├── build/                      # Compiled ABI + bytecode
├── src/
│   └── x402-client.js          # X402Client + X402Server classes
├── scripts/
│   ├── deploy.js               # Real deployment to Base Sepolia
│   └── proof-of-work.json      # On-chain transaction evidence
├── test/
│   └── integration.test.js     # 18 integration tests
└── examples/
    └── demo.js                 # Interactive demo (server + client)

Use Cases

Research Marketplace

Multiple agents offer different research at different price points. Other agents discover, pay for, and consume research autonomously.

API Monetization

Wrap any API as a paid x402 endpoint. Other agents pay per-call with USDC. No API keys, no rate limit negotiations — just money.

Premium Data Feeds

Real-time DeFi analytics, NFT market data, or protocol metrics — served behind a paywall that agents handle automatically.

Security & Safety

• Testnet only — All demonstrations use Base Sepolia
• No mainnet credentials — Code defaults to testnet addresses
• Wallet keys excluded — .gitignore prevents committing secrets
• Input validation — Payment amounts, addresses, and IDs are validated
• Expiry enforcement — Payments expire after 1 hour on-chain

Future Directions

• Subscription models — Recurring payments via ERC-3009 / Permit2
• Cross-chain payments — CCTP integration for multi-chain commerce
• Dynamic pricing — Demand-based pricing models
• Agent reputation — Quality scoring for content providers
• Content streaming — Pay-per-byte or pay-per-minute models

License

MIT

Built by BAiSED for the OpenClaw USDC Hackathon 2026