x402 in TypeScript & Node.js: call a paid API with @2sio/sdk

The @2sio/sdk TypeScript client wraps the x402 probe → sign → retry loop behind a typed method call. Works in Node and any modern JS runtime.

// npm i @2sio/sdk
import { TwoS } from '@2sio/sdk'

// Fund any EVM wallet with a little USDC on Base. No signup, no API key.
const client = new TwoS({ privateKey: process.env.EVM_PRIVATE_KEY as `0x${string}` })

const res = await client.weather.zip({ zip: '94103' })
console.log(res.data)          // real National Weather Service forecast
console.log(res.costUsd)       // what this call cost, in USDC
console.log(res.settlement?.txHash)  // on-chain settlement tx

import { TwoS } from '@2sio/sdk'

const client = new TwoS({ trial: true })   // no key needed
const res = await client.validate.iban({ iban: 'GB82WEST12345698765432' })
console.log(res.data)  // real result, marked meta.trial

FAQ

How do I call an x402 API in TypeScript or Node.js?

Install @2sio/sdk, construct new TwoS({ privateKey }) with an EVM wallet key, and call any endpoint method (e.g. client.weather.zip({ zip: "94103" })). The SDK performs the 402 payment flow automatically.

Can I use plain fetch instead of the SDK?

Yes. The flow is: fetch the URL, receive 402 with the PaymentRequirements, build a PAYMENT-SIGNATURE from the accepts entry using a wallet library, and refetch with that header. The SDK just does this for you.

Does it work with axios / other HTTP clients?

The payment is just an HTTP header, so any client works. The SDK uses fetch under the hood; you can replicate the same probe-and-retry with axios if you build the PAYMENT-SIGNATURE yourself.

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