underground.substratesymposium.com

x402 conformance verification for wallet developers. Pay $1.00 USDC on Base or Solana; receive an Ed25519-signed attestation that your client completed a real 402→auth→settle→deliver cycle on production infrastructure. Includes @maraventano/map decoder source (src/read.js) inline for URL parsing in future transactions. Use in CI pipelines, before SDK releases, or as agent-to-agent trust anchor.

Open endpoint ↗

Price per call: $1.00
Chain: Base
Method: GET
Paid calls · 30 days: 1

Call it from code

This API is run by its own provider and paid directly through x402. We list it so you can find it; we don't route or hold the payment.

import { x402Client, wrapFetchWithPayment } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";

const client = new x402Client();
registerExactEvmScheme(client, { signer: agentAccount });

const pay = wrapFetchWithPayment(fetch, client);
const res = await pay("https://underground.substratesymposium.com/api/merchant-key", { method: "GET" });
console.log(await res.json());

https://underground.substratesymposium.com/api/merchant-key