Charge for an HTTP endpoint. Or pay for one.

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 an EIP-3009 authorization for one of the offered terms, retry with it. You spend the stablecoin and nothing else — the gas is the facilitator's problem. Ask before you pay: /supported says whether this facilitator can settle that scheme on that network at all.

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.