Your first x402 integration.

You are selling

Your endpoint answers 402 with the terms you accept. The buyer signs one of them and retries with the signature in a header. Your middleware hands that to this facilitator: verify to check it, settle to put it on chain. You never touch a private key, never pay gas, and never wait for a block before answering.

Charging one route is this much code. The route and its price sit in the same file, three lines apart — here, five cents for /world:

// npm install hono @hono/node-server uvd-x402-sdk
import { Hono } from 'hono';
import { serve } from '@hono/node-server';
import { createHonoMiddleware } from 'uvd-x402-sdk';

const app = new Hono();

const paywall = createHonoMiddleware({
  accepts: [{
    network: 'base',
    asset: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913',
    amount: '50000',
    payTo: '0xYourWallet',
  }],
});

app.get('/world', paywall, (c) => c.json({ hello: 'world' }));

serve({ fetch: app.fetch, port: 3000 });

The same route in Python, where the price is a decorator on the view:

# pip install flask uvd-x402-sdk
from decimal import Decimal
from flask import Flask, jsonify
from uvd_x402_sdk.integrations import FlaskX402

app = Flask(__name__)
x402 = FlaskX402(app, recipient_address="0xYourWallet")

@app.route("/world")
@x402.require_payment(amount_usd=Decimal("0.05"))
def world():
    return jsonify({"hello": "world"})

The two say the price differently and both are right: the TypeScript middleware takes the on-chain integer, so five cents of a six-decimal USDC is 50000, while the Python decorator takes dollars and converts. Getting that wrong by a factor of a million is the second most common first-integration failure, after the domain name below.

For an axum server the same two calls are the x402-axum crate in this repository, with the middleware applied per route the same way.

The default facilitator in both SDKs is already this one. Nothing to configure until you want a different one.

You are buying

Read the 402, sign the offered network payment and retry with it. Arc uses direct EOA USDC authorizations; native Hedera uses a buyer-signed CryptoTransfer and x402 v2. The facilitator pays network fees. Check /supported for the exact network, asset, version and fee payer.

pip install uvd-x402-sdk
# or, for a reqwest client, the crate:
# x402-reqwest

If your client is an agent rather than a program, the same four calls are MCP tools at /mcp.