# 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
```bash
npm install
```
### 2. Configure Environment
```bash
export X402_WALLET=0xYourWalletAddress
```
### 3. Run the Server
```bash
# Development mode (without x402)
npm run dev
# Production mode (with x402)
npm run build
npm start
```
### 4. Test Endpoints
```bash
# 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`:
```typescript
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:
```json
{
"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](../../docs/content/x402-deploy/overview.md)
