x402 Content Gate

🚀 Monetize any AI agent's API endpoints instantly with USDC micropayments on Base

An OpenClaw skill and npm package that implements the x402 protocol for HTTP 402 Payment Required responses. Drop it into any Express app to start charging for API access using USDC on Base blockchain.

🎯 Features

• Zero-config setup - Just provide a wallet address
• USDC on Base - Fast, cheap transactions via x402 protocol
• Express middleware - Drop into any existing Node.js API
• TypeScript support - Fully typed for better DX
• Demo included - Working example with test client
• OpenClaw skill - Ready-to-use agent capability

🚀 Quick Start

Install

npm install @axiom/x402-gate

Basic Usage

import express from 'express';
import { x402Gate } from '@axiom/x402-gate';

const app = express();

// Configure payment gate
app.use(x402Gate({
  wallet: '0xYourWalletAddress',  // Where USDC payments go
  routes: {
    'GET /api/data': { price: '$0.01', description: 'Get data' },
    'POST /api/generate': { price: '$0.10', description: 'AI generation' },
  }
}));

// Your API routes (now monetized!)
app.get('/api/data', (req, res) => {
  res.json({ data: 'valuable information' });
});

app.listen(3000);

Client Usage

Use @x402/fetch to automatically handle payments:

import { x402Fetch } from '@x402/fetch';

// Client automatically pays and gets data
const response = await x402Fetch('http://localhost:3000/api/data');
const data = await response.json();

💡 How It Works

1. Client requests protected endpoint
2. Server responds with 402 Payment Required + payment details
3. Client pays USDC on Base via x402 facilitator
4. Server verifies payment and returns data
5. Everyone profits! 💰

🔧 Configuration

interface X402GateConfig {
  wallet: string;              // Your wallet address (required)
  routes: Record<string, {     // Route payment configuration
    price: string | number;    // '$0.01' or USDC units (10000)
    description: string;       // Human readable description
    facilitatorUrl?: string;   // Optional custom facilitator
  }>;
  chainId?: number;           // Default: 8453 (Base)
  usdcAddress?: string;       // Default: Base USDC contract
  debug?: boolean;            // Enable logging
}

Route Patterns

routes: {
  // Exact paths
  'GET /api/weather': { price: '$0.01', description: 'Weather data' },
  'POST /api/generate': { price: '$0.10', description: 'AI generation' },
  
  // Wildcards (future feature)
  'GET /api/data/*': { price: '$0.005', description: 'Any data endpoint' },
}

Price Formats

// USD strings (converted to USDC automatically)
price: '$0.01'    // 10,000 USDC units (6 decimals)
price: '$1.50'    // 1,500,000 USDC units

// Direct USDC units
price: 10000      // $0.01 USD
price: 1500000    // $1.50 USD

🎮 Try the Demo

git clone https://github.com/0xAxiom/axiom-public.git
cd axiom-public/agent-tools/skills/x402-gate

npm install
npm run build

# Start demo server
npm run demo

# Test in another terminal
npm run test-client

Visit http://localhost:3000 to explore the API and see payment requirements.

📚 Examples

AI Agent API

See examples/express-api.ts for a complete AI agent setup with:

• Data endpoints ($0.01-$0.02)
• AI services ($0.03-$0.10)
• Premium features ($0.25-$0.50)
• Free public endpoints

OpenClaw Skill

This package includes an OpenClaw skill for easy agent integration. See SKILL.md for usage instructions.

🔒 Security

• No private keys - Only wallet addresses are stored
• Payment verification - All payments verified via x402 facilitator
• Error handling - Graceful failure modes
• Rate limiting - Use with express-rate-limit for additional protection

🌐 Protocol Details

Built on x402 by Coinbase:

• Chain: Base (8453)
• Token: USDC (0x833589fcd6edb6e08f4c7c32d4f71b54bda02913)
• Facilitator: https://x402.org/facilitator
• Standard: HTTP 402 Payment Required

🛠 API Reference

x402Gate(config)

Express middleware that protects routes with payment requirements.

verifyPayment(hash, payment, facilitator)

Verify a payment hash with the x402 facilitator.

parsePriceToUsdc(price)

Convert price strings to USDC units.

formatUsdcToPrice(usdc)

Format USDC units as human-readable prices.

🤝 Contributing

Built for the USDC Agent Hackathon. Contributions welcome!

1. Fork the repo
2. Make your changes
3. Add tests
4. Submit a PR

📄 License

MIT License - see LICENSE file for details.

🔗 Links

• x402 Protocol
• Base Network
• USDC Agent Hackathon
• Axiom GitHub

Made with ⚡ by Axiom for the agent economy