x402 on Robinhood Chain, open.

Behind the gateway

Paid calls reach your API with two extra headers: X-X402Fi-Secret (from your listing) and X-X402Fi-Payer. Check the secret so the paywall can't be bypassed.

// Your API, behind the x402Fi gateway: reject calls that skip the paywall.
app.use((req, res, next) => {
  if (req.get("x-x402fi-secret") !== process.env.X402FI_SECRET) return res.status(403).end();
  // Optional: who paid for this call
  req.payer = req.get("x-x402fi-payer");
  next();
});

Facilitator

x402 v2, scheme exact, network eip155:4663, asset USDG. x402Fi pays the gas for settlement and never holds funds.

• POST /api/facilitator/verify
• POST /api/facilitator/settle
• GET /api/facilitator/supported

// Self-hosted paywall that uses the x402Fi facilitator (Robinhood Chain, USDG).
const FACILITATOR = "https://x402fi.dev/api/facilitator";
const requirements = {
  scheme: "exact",
  network: "eip155:4663",
  amount: "10000",                      // 0.01 USDG (6 decimals); x402Fi minimum
  asset: "0x5fc5360D0400a0Fd4f2af552ADD042D716F1d168",
  payTo: "0xYourWallet",
  maxTimeoutSeconds: 120,
  extra: { name: "Global Dollar", version: "1" },
};

app.get("/rates", async (req, res) => {
  const header = req.get("payment-signature") ?? req.get("x-payment");
  if (!header) {
    const pr = { x402Version: 2, resource: { url: req.url, description: "FX rates", mimeType: "application/json" }, accepts: [requirements] };
    return res.status(402).set("PAYMENT-REQUIRED", Buffer.from(JSON.stringify(pr)).toString("base64")).json(pr);
  }
  const paymentPayload = JSON.parse(Buffer.from(header, "base64").toString());
  const body = JSON.stringify({ paymentPayload, paymentRequirements: requirements });
  const v = await fetch(FACILITATOR + "/verify", { method: "POST", headers: { "content-type": "application/json" }, body }).then(r => r.json());
  if (!v.isValid) return res.status(402).json({ error: v.invalidReason });

  const data = await computeRates();                         // do the work
  const s = await fetch(FACILITATOR + "/settle", { method: "POST", headers: { "content-type": "application/json" }, body }).then(r => r.json());
  if (!s.success) return res.status(402).json({ error: s.errorReason });
  res.set("PAYMENT-RESPONSE", Buffer.from(JSON.stringify(s)).toString("base64")).json(data);
});

Discovery

Every paid endpoint is published in a Bazaar-style feed that agents and indexers can crawl: /api/discovery/resources (JSON), with a readable view at /discovery.

Verified payee

// Name the payee in your 402 so agents can verify you (x402 payee-name extension)
"extensions": { "payee-name": { "info": { "name": "yourco.402api.eth" } } }

// Agents check it with:
import { verifyPayee, viemReader } from "@x402identity/payee";
const verdicts = await verifyPayee(paymentRequired, origin, viemReader(mainnetClient));

Spec: payee-name extension. Records: org.x402.origins and the Robinhood Chain address (coin type 2147488311).

USDG details

Address

0x5fc5360D0400a0Fd4f2af552ADD042D716F1d168

Decimals

6

EIP-712 domain

name "Global Dollar", version "1", chainId 4663

Transfer

transferWithAuthorization (EIP-3009, v/r/s)