paid-api

Paid API Example

A cryptocurrency data API that accepts x402 payments.

Features

Free Endpoints

• GET /api/health - Health check

Basic Paid Endpoints ($0.0001 - $0.0005)

• GET /api/v1/price/:symbol - Get current price
• GET /api/v1/prices - Get all prices
• GET /api/v1/trending - Get trending coins

Premium Endpoints ($0.01 - $0.05)

• GET /api/v1/premium/analysis/:symbol - Detailed technical analysis
• GET /api/v1/premium/signals - Trading signals

Quick Start

1. Install Dependencies

npm install

2. Configure Environment

export X402_WALLET=0xYourWalletAddress

3. Run the Server

# Development mode (without x402)
npm run dev

# Production mode (with x402)
npm run build
npm start

4. Test Endpoints

# Free endpoint
curl http://localhost:3000/api/health

# Paid endpoint (will return 402 when x402 is enabled)
curl http://localhost:3000/api/v1/price/BTC

Enabling x402 Payments

Uncomment the x402 wrapper in src/index.ts:

import { wrapExpressWithX402 } from "@nirholas/x402-deploy/express";
import config from "./x402.config.json";

// ... your routes ...

const wrappedApp = wrapExpressWithX402(app, config);
wrappedApp.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
});

Configuration

Edit x402.config.json to customize:

• Wallet address: Where payments go
• Network: Which blockchain (Arbitrum, Base, etc.)
• Pricing: Cost per endpoint
• Discovery: How AI agents find your API

How It Works

1. Client requests a paid endpoint
2. Server returns 402 Payment Required with payment details
3. Client makes payment via x402 protocol
4. Client retries with X-PAYMENT header
5. Server verifies payment and returns data

Testing with AI Agents

Configure Claude Desktop with x402 support:

{
  "mcpServers": {
    "universal-crypto": {
      "command": "npx",
      "args": ["@nirholas/universal-crypto-mcp"],
      "env": {
        "X402_PRIVATE_KEY": "0xYourPrivateKey"
      }
    }
  }
}

Then ask Claude:

"Get the BTC analysis from http://localhost:3000/api/v1/premium/analysis/BTC"

Claude will:

1. Make the request
2. See the $0.01 cost
3. Ask for confirmation
4. Make the payment
5. Return the analysis

Project Structure

paid-api/
├── src/
│   └── index.ts        # API server
├── x402.config.json    # x402 configuration
├── package.json        # Dependencies
└── README.md           # This file

Next Steps

• Deploy to Vercel/Railway
• Add more premium endpoints
• Set up analytics dashboard
• See x402-deploy docs