Pay for the outcome.
One endpoint for every model, tool and data source an agent needs — priced in dollars before it runs, settled in USDC on Arc through Circle. A wallet holding USDC on Arc is the only account. No gas per call.
A wallet with USDC on Arc. That is the whole setup.
Any wallet you already control. USDC is Arc's native token, so there is nothing else to acquire — and you never spend it on gas here.
Call the endpoint. It answers 402 with the price in dollars and an Arc payment requirement: USDC, the amount, where it goes.
Sign an EIP-3009 authorization for exactly that amount and send the call again. Circle verifies and settles it on Arc. 105 models and every tool, one endpoint.
// 1. Ask. The 402 carries the requirement (network, asset, amount, payTo).
const res = await fetch("https://arc.blockrun.ai/v1/chat/completions", { method: "POST", body });
const { accepts: [req] } = JSON.parse(atob(res.headers.get("PAYMENT-REQUIRED")));
// 2. Sign — EIP-3009 transferWithAuthorization against USDC on Arc.
const authorization = { from: me, to: req.payTo, value: req.amount, validAfter: 0n,
validBefore: now + 300n, nonce: randomBytes32() };
const signature = await wallet.signTypedData({
domain: { name: "USDC", version: "2", chainId: 5042,
verifyingContract: "0x3600000000000000000000000000000000000000" },
types, primaryType: "TransferWithAuthorization", message: authorization });
// 3. Retry with the signed authorization. Circle settles it on Arc.
await fetch(res.url, { method: "POST", body, headers: {
"PAYMENT-SIGNATURE": btoa(JSON.stringify({ x402Version: 2, accepted: req,
payload: { signature, authorization } })) } });Nobody ships one
model in production.
The combination is the hard part to buy. Here it is one endpoint, whichever pieces you need.
Quotes, odds and on-chain positions, read in one session.
The clip is one model. The score, the voice and the thumbnail are three more.
Neural search for the answer, live search for this morning, one model to read both.
A real number, a voice worth hearing, and a model deciding what to say.
What it costs to call one.
Claude Fable 5.1Claude Fable 5
GPT-5.6 SolClaude Opus 5Watch an agent
pay its way.
An agent on this endpoint. It asks, the call is priced before it runs, and it signs for it — a wallet with USDC on Arc, nothing else.
