Guide · Pay from Robinhood Chain

Pay from Robinhood Chain

A buyer on Robinhood Chain pays for inference with the USDG it already holds on Robinhood Chain. Each call is paid with x402, with no key, no gas and no account with us.

The path

1. Hold USDG on Robinhood Chain

USDG on Robinhood Chain at the buyer's own address. no move: the door settles exact on Robinhood Chain in USDG.

2. Call, paid with x402

Without a key the call answers 402. The PAYMENT-REQUIRED header holds the terms: one exact entry per network the door settles, the amount, and the address that is paid. Pick the entry for eip155:4663 (Robinhood Chain, USDG). You never type the payee: it is read from the challenge.

curl -i -X POST https://coord.taifoon.dev/v1/chat/completions \
  -H "content-type: application/json" \
  -d '{"model":"llama-3.3-70b","messages":[{"role":"user","content":"hello"}],"max_tokens":64}'

Any x402 v2 client pays it. In TypeScript, with the key of the address that holds the USDG:

import { wrapFetchWithPaymentFromConfig } from '@x402/fetch';
import { ExactEvmScheme } from '@x402/evm';
import { privateKeyToAccount } from 'viem/accounts';

const account = privateKeyToAccount(process.env.EVM_PRIVATE_KEY as `0x${string}`);
const pay = wrapFetchWithPaymentFromConfig(fetch, {
  schemes: [{ network: 'eip155:4663', client: new ExactEvmScheme(account) }],
});

const r = await pay('https://coord.taifoon.dev/v1/chat/completions', {
  method: 'POST',
  headers: { 'content-type': 'application/json' },
  body: JSON.stringify({"model":"llama-3.3-70b","messages":[{"role":"user","content":"hello"}],"max_tokens":64}),
});
console.log(await r.json()); // an OpenAI chat completion

The client signs one transfer authorization (EIP-3009). The facilitator settles it and pays the gas, so the address holds the dollar token only.

A key is free and not needed to pay with x402. A call sent with a key is paid from that key's balance; a call sent without one is paid with x402. Each model also has its own path, /v1/chat/completions/<model>. Prices lists every priced wall.

What it takes

• USDG on Robinhood Chain at an address the buyer signs for

Nothing from Taifoon: no key, no registration, no account and no spec before the first paid call. The money lands per call in vault:taifoon:kms.

How this was checked

the door's 402 challenge offers exact on eip155:4663 (read 2026-10-22T18:04:25Z). Proven by a quote or a challenge: yes. Quotes and challenges only: nothing was deposited, signed or paid to check this page.