Signal Desk

Pay-per-call tools for AI agents, paid in USDC on Base through x402. No account and no API key: the first call answers 402 Payment Required with the price, the agent's wallet signs a transfer for exactly that amount, and the second call gets the result plus a receipt. Settlement happens only after the work succeeded, so a call the service refuses is never charged.

Every route's fields, limits and an example are in its 402 answer and in GET / on the HTTP host. Every refusal (bad input, private address, executable upload) carries the same usage object, free.

Use it

Use a throwaway wallet holding a few cents of USDC on Base, never a main wallet.

Any HTTP client

import { x402Client } from "@x402/core/client";
import { toClientEvmSigner } from "@x402/evm";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { wrapFetchWithPayment } from "@x402/fetch";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
registerExactEvmScheme(client, {
  signer: toClientEvmSigner(privateKeyToAccount(process.env.X402_PRIVATE_KEY)),
});
const payingFetch = wrapFetchWithPayment(fetch, client);

const res = await payingFetch("https://x402-paywall.huntercarver24.workers.dev/render", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({ url: "https://example.com", format: "markdown" }),
});
console.log(res.status, await res.text());

npm install @x402/core @x402/evm @x402/fetch viem, Node 20 or later, saved as an .mjs file.

Claude Code

claude plugin marketplace add huntercarver24/signal-desk
claude plugin install x402-pay@signal-desk
export X402_PRIVATE_KEY=0x...

The x402-pay skill teaches Claude the five routes and pays them with scripts/pay.mjs. Claude says the price before the first paid call, and each payment runs as a command you approve.

MCP clients that pay x402

An MCP client needs x402 support to pay; any other client still lists the tools and sees each price in a payment-required result. With @x402/mcp:

import { Client } from "@modelcontextprotocol/sdk/client/index.js";
import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js";
import { x402Client } from "@x402/core/client";
import { toClientEvmSigner } from "@x402/evm";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { wrapMCPClientWithPayment } from "@x402/mcp";
import { privateKeyToAccount } from "viem/accounts";

const mcp = new Client({ name: "my-agent", version: "1.0.0" });
await mcp.connect(
  new StreamableHTTPClientTransport(new URL("https://x402-mcp.huntercarver24.workers.dev/feeds/mcp"))
);
const payment = new x402Client();
registerExactEvmScheme(payment, {
  signer: toClientEvmSigner(privateKeyToAccount(process.env.X402_PRIVATE_KEY)),
});
const paying = wrapMCPClientWithPayment(mcp, payment);

const result = await paying.callTool("trending_topics", { hours: 6, limit: 10 });
console.log(result.content[0].text);

npm install @modelcontextprotocol/sdk @x402/core @x402/evm @x402/mcp viem.

OpenCode

mkdir -p .opencode/plugins && curl -fsSL https://raw.githubusercontent.com/huntercarver24/signal-desk/main/opencode/x402-tools.ts -o .opencode/plugins/x402-tools.ts

Then add the dependencies listed in opencode/package.json to .opencode/package.json; OpenCode installs them at startup. The agent gets the five tools.

Related MCP server: Ausca

House rules

• A refused call costs nothing. Neither does a feed that has fallen behind its source: it answers 503 with retry-after instead of charging for stale data.

• The launch feed and the trend radar are data only. Nothing in them rates, recommends or trades a token. Sports topics and markets are filtered out, by keywords and by a model check on each topic before it is shown.

• No caller has an account, so nothing is stored about you beyond the payment on chain. Hosted files expire at the time you choose.

Status

monitor/check.mjs probes every surface a paying agent touches, for free, every 15 minutes: the paywall's health and configuration, a live 402 with its terms, the trend sources' freshness, the launch feed's lag, and both MCP endpoints. The badge above is its latest result.

Known issue: the launch feed's Solana data provider has blocked the project since October 29, 2026. Until that clears, POST /launches and recent_launches refuse with a free 503; the other four tools are unaffected.

License

MIT. The services themselves are run by Hunter Carver; this repository holds the clients, the uptime check and these docs.