x402node

Install (JS / TypeScript)

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("0xYOUR_KEY");
const wallet  = createWalletClient({ account, chain: base, transport: http() });
const pay     = wrapFetchWithPayment(fetch, wallet);

const r = await pay("https://api.x402node.dev/chain/tx-decode?tx=0x...");
console.log(await r.json());   // 402 -> auto-sign EIP-3009 -> 200 + data

Inspect from the command line

curl -i https://api.x402node.dev/dev/uuid
# HTTP/1.1 402 Payment Required
# the body carries the x402 payment terms (network, amount, asset)
# a paying client signs EIP-3009 and retries with the X-PAYMENT header

Any x402-capable client or agent works — the protocol is plain HTTP. Python client and MCP server are on the way.