The First x402 Payment API

Authentication

AsterPay uses one rule per surface. You almost never need an API key.

Live payout requires KYB (handled at settlement, not at the API). Reads and per-call payments stay keyless and accountless.

Example Usage

// FREE read endpoint — no key, no payment
const est = await fetch(
  'https://x402.asterpay.io/v1/settlement/estimate?amount=100'
).then(r => r.json());
console.log(est.data.netEurAmount, est.data.estimatedSepaTime);

// PAID endpoint — easiest path is the x402 fetch wrapper, which
// auto-handles the 402 -> pay -> retry loop for you.
// npm install x402-fetch   (USDC on Base, EIP-3009, mainnet)
import { wrapFetchWithPayment } from 'x402-fetch';
import { account } from './wallet.js'; // your funded signer

const pay = wrapFetchWithPayment(fetch, account);

const data = await pay(
  'https://x402.asterpay.io/v1/agent/deep-analysis/0xYourAgentAddress'
).then(r => r.json());
// The wrapper reads the 402 challenge (x402Version 2, network eip155:8453,
// USDC asset), signs an EIP-3009 transferWithAuthorization, base64-encodes it,
// and retries with the PAYMENT-SIGNATURE header. You just get the result.

Prefer raw HTTP or another language? The full request/response shapes are in the OpenAPI 3.1 spec, the Postman collection, and the interactive docs. Every paid call also accepts MPP (Authorization: Payment) on the same URL.