Documentation

Monetize Your API in Minutes

Production-ready integration guide for xMCPKit and x402 payment protocol

Quick Start

Install the x402 SDK

bash

npm install x402-sdk
# or
yarn add x402-sdk

Add x402 Middleware

typescript

import express from 'express';
import { x402PaymentMiddleware } from 'x402-sdk';

const app = express();

// Add payment middleware
app.use(x402PaymentMiddleware({
  walletAddress: '0xYourSOLWallet',
  pricePerCall: 0.001,
  network: 'solana',
  currency: 'SOL'
}));

// Your API endpoints
app.get('/api/data', (req, res) => {
  res.json({ message: 'Paid access granted!' });
});

app.listen(3000);

Configure Your Wallet

Set up a Solana wallet to receive SOL payments:

bash

# Generate a new wallet (or use existing)
solana-keygen new --outfile ~/.config/solana/xmcpkit-wallet.json

# Get your public address
solana address

# Fund it with SOL for transaction fees
solana airdrop 1

Enable MCP Discovery

Add an MCP manifest so AI agents can discover your API:

json

{
  "name": "My API",
  "version": "1.0.0",
  "description": "Sentiment analysis API",
  "endpoints": [
    {
      "path": "/api/sentiment",
      "method": "POST",
      "price": 0.001,
      "currency": "SOL",
      "description": "Analyze text sentiment"
    }
  ],
  "payment": {
    "protocol": "x402",
    "wallet": "0x7a3f...9d2c",
    "network": "solana"
  }
}

How x402 Protocol Works

Client Makes Request

An AI agent or client sends a request to your API endpoint

POST /api/sentiment

Server Returns 402

Your API responds with payment requirements

HTTP 402 Payment Required
x402-PayTo: usdc:0x7a3f...9d2c
x402-Amount: 0.001
x402-Network: solana

Client Pays

The agent automatically sends SOL to your wallet

0.001 SOL → 0x7a3f...9d2c

Access Granted

Your API verifies payment and returns the response

HTTP 200 OK
{ "sentiment": "positive", "score": 0.95 }

Framework Examples

Express.js

typescript

import express from 'express';
import { x402Middleware } from 'x402-sdk';

const app = express();

app.use('/api/*', x402Middleware({
  wallet: '0xYourWallet',
  price: 0.001
}));

app.post('/api/translate', (req, res) => {
  // Your translation logic
  res.json({ translated: "Hola" });
});

Next.js API Route

typescript

import { NextRequest, NextResponse } from 'next/server';
import { verifyX402Payment } from 'x402-sdk';

export async function POST(req: NextRequest) {
  // Check payment
  const payment = await verifyX402Payment(req, {
    wallet: '0xYourWallet',
    amount: 0.001
  });

  if (!payment.verified) {
    return NextResponse.json(
      { error: 'Payment required' },
      { 
        status: 402,
        headers: {
          'x402-PayTo': 'usdc:0xYourWallet',
          'x402-Amount': '0.001'
        }
      }
    );
  }

  return NextResponse.json({ data: "Success" });
}

Testing Your API

Use AgentKit to test your monetized API:

bash

# Install AgentKit CLI
npm install -g agentkit

# Test your API
agentkit call \
  --url http://localhost:3000/api/sentiment \
  --wallet ~/.config/solana/test-wallet.json \
  --data '{"text": "I love this!"}' \
  --auto-pay

# Output:
# ✓ Payment sent: 0.001 SOL
# ✓ Response: { "sentiment": "positive", "score": 0.95 }

Ready to Monetize Your API?

Explore the marketplace or deploy your own API