x402 in 5 minutes

1 · The flow

Client  --GET /resource-->  Server
Client  <--402 + terms----  Server   (price, token, address, network)
Client  --pay USDC on Base + retry with X-PAYMENT header-->  Server
Client  <--200 + data------  Server

2 · Call your first paid API (JavaScript)

npm i x402-fetch viem

import { wrapFetchWithPayment } from "x402-fetch";
import { createWalletClient, http } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { base } from "viem/chains";

const account = privateKeyToAccount(process.env.PRIVATE_KEY); // a wallet with a little USDC on Base
const wallet  = createWalletClient({ account, chain: base, transport: http() });
const pay     = wrapFetchWithPayment(fetch, wallet);

const res = await pay("https://x402.tavily.com/search?query=x402", { method: "GET" });
console.log(await res.json()); // paid, retried, done

3 · Fund a wallet

Create any EVM wallet, hold a few dollars of USDC on Base for the calls and a little ETH on Base for gas (often sponsored). Most services cost $0.001 – $0.01 per call, so a few dollars goes a long way.

4 · Find a service

Browse the catalog and open any service for ready-to-run JavaScript, Python and curl. Every page is generated from the live on-chain registry.