# 💰 x402 Payment Protocol Integration
> **For: [Universal Crypto MCP](https://github.com/nirholas/universal-crypto-mcp)**
## 💰 Give Claude Money!
```bash
npx @nirholas/universal-crypto-mcp
```
x402 is an open standard for internet-native payments built on HTTP 402. This integration enables AI agents to autonomously pay for API access.
**Target Repository:** https://github.com/nirholas/universal-crypto-mcp
## 🚀 Quick Start
### For Buyers (AI Agents Making Payments)
```typescript
import { wrapAxiosWithPayment, x402Client } from "@x402/axios";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";
import axios from "axios";
// Create wallet signer
const signer = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${string}`);
// Create x402 client with EVM support
const client = new x402Client();
registerExactEvmScheme(client, { signer });
// Wrap axios - payments handled automatically!
const api = wrapAxiosWithPayment(axios.create({ baseURL: "https://api.example.com" }), client);
// This will auto-pay if API returns 402
const response = await api.get("/paid-endpoint");
```
### For Sellers (APIs Receiving Payments)
```typescript
import express from "express";
import { paymentMiddleware } from "@x402/express";
import { x402ResourceServer, HTTPFacilitatorClient } from "@x402/core/server";
import { registerExactEvmScheme } from "@x402/evm/exact/server";
const app = express();
const facilitator = new HTTPFacilitatorClient({ url: "https://x402.org/facilitator" });
const server = new x402ResourceServer(facilitator);
registerExactEvmScheme(server);
app.use(paymentMiddleware({
"GET /api/data": {
accepts: [{
scheme: "exact",
price: "$0.001",
network: "eip155:8453", // Base Mainnet
payTo: "0xYourAddress",
}],
description: "Premium API data",
},
}, server));
app.get("/api/data", (req, res) => {
res.json({ data: "premium content" });
});
```
## 📦 Installation
```bash
# Core packages
npm install @x402/core @x402/evm @x402/svm
# For HTTP clients
npm install @x402/axios @x402/fetch
# For servers
npm install @x402/express @x402/hono @x402/next
# Wallet support
npm install viem @solana/kit @scure/base
```
## 🔗 Supported Networks (CAIP-2 Format)
### EVM Networks
| Network | CAIP-2 ID | Token |
|---------|-----------|-------|
| Base Mainnet | `eip155:8453` | USDC |
| Base Sepolia | `eip155:84532` | USDC |
| Ethereum | `eip155:1` | USDC |
| Arbitrum One | `eip155:42161` | USDC |
| Polygon | `eip155:137` | USDC |
| Optimism | `eip155:10` | USDC |
| BNB Chain | `eip155:56` | USDC |
### Solana Networks
| Network | CAIP-2 ID | Token |
|---------|-----------|-------|
| Mainnet | `solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp` | USDC |
| Devnet | `solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1` | USDC |
## 🤖 MCP Server Integration
Enable Claude and other AI agents to pay for APIs:
```typescript
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import axios from "axios";
import { x402Client, wrapAxiosWithPayment } from "@x402/axios";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";
const signer = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${string}`);
const client = new x402Client();
registerExactEvmScheme(client, { signer });
const api = wrapAxiosWithPayment(axios.create({ baseURL: process.env.API_URL }), client);
const server = new McpServer({ name: "x402-mcp", version: "2.0.0" });
server.tool("get-paid-data", "Fetch premium data (auto-pays)", {}, async () => {
const res = await api.get("/premium");
return { content: [{ type: "text", text: JSON.stringify(res.data) }] };
});
const transport = new StdioServerTransport();
await server.connect(transport);
```
### Claude Desktop Configuration
```json
{
"mcpServers": {
"universal-crypto-mcp": {
"command": "npx",
"args": ["@nirholas/universal-crypto-mcp"],
"env": {
"EVM_PRIVATE_KEY": "0x...",
"RESOURCE_SERVER_URL": "https://api.example.com"
}
}
}
}
```
## 📄 How It Works
```
┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐
│ Claude / Agent │────▶│ MCP Server │────▶│ x402 API │
│ │ │ (x402 client) │ │ (paid endpoint)│
└─────────────────┘ └─────────────────┘ └─────────────────┘
│ │ │
│ 1. Call tool │ 2. GET /api │
│ │ │
│ │ 3. 402 + payment req │
│ │◀──────────────────────│
│ │ │
│ │ 4. Sign payment │
│ │ │
│ │ 5. Retry w/ payment │
│ │──────────────────────▶│
│ │ │
│ │ 6. 200 + data │
│ │◀──────────────────────│
│ │ │
│ 7. Return response │ │
│◀──────────────────────│ │
```
## 🔧 Environment Variables
```bash
# Required for buyers
EVM_PRIVATE_KEY=0x... # EVM wallet private key
SVM_PRIVATE_KEY=... # Solana wallet (optional)
# Required for sellers
EVM_ADDRESS=0x... # Receiving address
FACILITATOR_URL=https://x402.org/facilitator
# Network selection
DEFAULT_NETWORK=eip155:8453 # Base Mainnet
```
## 📚 Documentation
- [MCP Server Guide](./docs/guides/mcp-server-with-x402.md)
- [Quickstart for Buyers](./docs/getting-started/quickstart-for-buyers.mdx)
- [Quickstart for Sellers](./docs/getting-started/quickstart-for-sellers.mdx)
- [LLMs Full Documentation](./docs/llms-full.md)
- [CAIP-2 Network IDs](./docs/CAIP-2.md)
- [Core Concepts](./docs/core-concepts/)
## 🔗 Resources
- **x402 Protocol**: https://x402.org
- **Documentation**: https://docs.x402.org
- **GitHub**: https://github.com/coinbase/x402
- **Discord**: https://discord.gg/cdp
## ⚖️ License
x402 is licensed under Apache-2.0. See [LICENSE](./LICENSE) for details.
---
**💰 Give Claude Money!**
```bash
npx @nirholas/universal-crypto-mcp
```
