Penniless Data Utilities MCP Server

Penniless Data Utilities

Nine deterministic data and lookup tools for AI agents, paid per call in USDC. REST advertises both native MPP and x402; MCP uses x402 v2. No accounts, no API keys, no rate-limit tiers. Every tool is pure computation or a keyless public lookup — none of them call another AI model, so results are reproducible.

• Live endpoint (MCP): https://penniless-json-repair.sjaman.workers.dev/mcp
• Live endpoint (REST): https://penniless-json-repair.sjaman.workers.dev
• Discovery: /health, /openapi.json, /llms.txt, /.well-known/x402

Pricing

$0.001 USDC per call. REST advertises native MPP plus x402 v2 (eip155:8453, scheme exact); MCP uses x402 v2.

Base x402 settlements are verified by the free-tier PayAI facilitator. Native MPP is negotiated by mppx. Recipient (payTo): 0x3D98800c64C345950E1eAaa076D88C12d1BF5F37.

Connect over MCP

Any MCP client that speaks streamable HTTP can connect directly:

{
  "mcpServers": {
    "penniless-data-utilities": {
      "type": "http",
      "url": "https://penniless-json-repair.sjaman.workers.dev/mcp"
    }
  }
}

The transport is stateless — no session id is issued or required, and every request is independent. initialize and tools/list are free. An unpaid tools/call returns an x402 payment-required payload in result.content[0].text (and result.structuredContent); attach the signed payment as params._meta["x402/payment"] and repeat the call.

If you use an x402-aware MCP client, @x402/mcp handles that exchange for you.

Tools

POST /diagnose is free: it classifies what is wrong with a malformed JSON payload without returning the repaired output, so a caller can check whether paying is worthwhile before paying.

Example (REST + x402 client)

Any x402 v2 client works. With the reference TypeScript client and a viem account:

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

const client = new x402Client();
registerExactEvmScheme(client, { signer: privateKeyToAccount(key), networks: ["eip155:8453"] });
const pay = wrapFetchWithPayment(fetch, client);

const res = await pay("https://penniless-json-repair.sjaman.workers.dev/repair/json", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({ input: "{foo: 'bar',}" }),
});
// -> { ok: true, repaired: { foo: "bar" }, applied: ["unquoted-keys","single-quotes","trailing-commas"] }

wrapFetchWithPayment handles the 402 round-trip: it receives the requirement, signs the USDC authorization, retries, and only returns a 200 once the facilitator has settled.

Development

npm install
npm test        # 133 tests, runs fully offline (facilitator + upstream are injected)
npx wrangler dev
npx wrangler deploy

Environment (set in wrangler.toml): X402_NETWORK, X402_FACILITATOR, X402_PRICE, X402_PAY_TO. Production also has an encrypted Cloudflare secret MPP_SECRET_KEY used only to authenticate MPP challenges. Wallet private keys are never deployed to the Worker.

Maintainer

GitHub: @danielarif26