x402 Monetization

Monetize MCP tools with x402 using USDC micropayments on Base.

Features

• x402 payment middleware for per-tool pricing
• Free and paid tools in the same server
• Custom price overrides per tool
• USDC payments on Base (Sepolia for testing, mainnet for production)
• Example tools: greet (paid, $0.01), hash-string (paid, $0.05), random-number (free)

Getting Started

Prerequisites

You need a wallet address to receive USDC payments.

1. Create the project

npx create-xmcp-app --example x402

2. Environment setup

cp .env.example .env

Edit .env with your wallet address:

X402_WALLET=0xYOUR_WALLET_ADDRESS

# Optional: custom facilitator URL
# X402_FACILITATOR=https://x402.org/facilitator

3. Install & run

pnpm install
pnpm dev

How It Works

The middleware is configured in src/middleware.ts with default pricing:

• Default price: 0.01 USDC per tool call
• Currency: USDC
• Network: base-sepolia (switch to base for production)
• Facilitator: https://x402.org/facilitator

Making Tools Paid

Wrap tools with paid() from @xmcp-dev/x402:

import { paid } from "@xmcp-dev/x402";

// Uses middleware default price ($0.01)
export default paid(async function greet({ name }) {
  return `Hello, ${name}!`;
});

// Custom price override ($0.05)
export default paid(
  { price: 0.05 },
  async function hashString({ input }) {
    const encoder = new TextEncoder();
    const data = encoder.encode(input);
    const hashBuffer = await crypto.subtle.digest("SHA-256", data);
    const hashArray = Array.from(new Uint8Array(hashBuffer));
    return hashArray.map((b) => b.toString(16).padStart(2, "0")).join("");
  }
);

Tools without the paid() wrapper are free.

Deploy

pnpm build
node dist/http.js

For production, update your middleware to use base instead of base-sepolia.

Learn More

• xmcp Documentation
• x402 Integration Guide