Lumière PayCheck

Lumière PayCheck

Check an x402 endpoint before your agent pays it.

AI agents now pay for APIs on their own with x402: an endpoint answers 402 Payment Required with a price, the agent pays in USDC, and gets the data. Nothing in that flow tells the agent whether the endpoint works, whether the price is right, or whether the payout wallet is the real one.

Lumière PayCheck answers those questions. It monitors every endpoint listed in the x402 Bazaar, grades each one, and gives your agent a plain verdict: proceed, caution, or avoid.

🌐 Live: https://lumierepaycheck.org · 🔌 MCP: https://lumierepaycheck.org/mcp?plans=1 · 📜 Terms

This repository is the public home for docs, examples, and feedback. The monitoring service itself is hosted and closed-source; the scoring formula is public (below).

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What it does

• Monitors every endpoint in the x402 Bazaar (the badge above shows the live count, which grows as new endpoints are listed) every 30 minutes: price quote, payout wallet, uptime, response time.
• Flags hijack risk, without punishing normal rotations. Every payout-wallet change is checked against the seller's own wallet declaration, the seller's earlier wallets, and direct transfers between the old and new wallet. Confirmed rotations don't affect the grade; unexplained changes are avoid, then caution with human review. Sellers that use a new address per request are recognized automatically. How it works.
• Spending rules for agents. Before paying, an agent asks "may I pay *this* endpoint *this* amount to *this* wallet?" and gets allow or deny with reasons.
• Plans for teams. Scoped agent keys, daily/monthly spend limits, signed receipts your wallet verifies before paying, a replayable audit trail, and human review for anomalies. Details.
• Identity and access for agents that pay. Like Entra ID and Intune, for AI agents:

API · Administrator guide

• Screening for facilitators. x402 facilitators can screen each payment before they settle it: OFAC sanctions on payer and payee, a payTo that isn't the seller's monitored or declared wallet, a price above the quote. 10,000 checks a month free. Details.
• Wallet risk. Before paying any wallet: OFAC sanctions screening, payout-wallet history, and possible-hijack signals in one paid call.
• Alerts. Watch an endpoint and get signed webhook alerts when it breaks, changes wallet, or raises its price.
• Paid delivery checks: small real payments that confirm an endpoint returns what it advertises. A failure only counts if a re-test about two hours later fails too, and requests an endpoint rejects for missing input never count.
• Known-answer tests: values, not just shape. Uptime and schema checks can pass while an API returns the wrong number. For endpoints with a knowable answer, the verifier pays for a call with a known correct result, or compares against an independent live source, and checks the value itself. Sellers can add their own tests. How it works.
• Real usage from on-chain data: actual x402 payments (USDC on Base and Solana) into each endpoint's payout wallet over 30 days: volume, distinct buyers, typical and largest payment, trend, and how concentrated the buyers are, counting only payments submitted by recognized facilitators.
• Buyer reports: after paying, any agent answers five short questions (with a receipt, or the payment transaction, verified on-chain; one line with the npm package: reportOutcome({ url, response, answers })). Confirmations move an endpoint up our paid-test queue and serious problems trigger a re-test; grades change only when our own paid test confirms.

No accounts, no API keys. Free checks are free; paid features are paid per call with x402, the same way agents pay everything else.

Quick start

1. From Claude, Cursor, or any MCP client

Add the remote MCP server:

https://lumierepaycheck.org/mcp?plans=1

• Claude: Settings → Connectors → Add custom connector → paste the URL.
• Cursor / others (mcp.json):

  { "mcpServers": { "lumiere-paycheck": { "url": "https://lumierepaycheck.org/mcp?plans=1" } } }

Tools: check_payment, check_endpoint, report_outcome, top_endpoints, catalog_stats, get_full_report.

Prefer a local stdio server? packages/mcp-server runs the same tools on your machine (node server.js, or the repo's Dockerfile).

2. Drop-in for the x402 fetch client (npm)

npm i x402-paycheck @x402/fetch

import { x402Client, wrapFetchWithPayment } from "@x402/fetch";

import { withPayCheck } from "x402-paycheck";

const fetchWithPay = wrapFetchWithPayment(fetch, withPayCheck(new x402Client().register(/* your scheme */)));

Every payment is checked by PayCheck before it's signed; a "no" aborts it with the reason. Details: packages/x402-paycheck.

Then add one rule to your agent's instructions:

Before paying any x402 endpoint, call the Lumière PayCheck check_payment tool with the endpoint URL, the amount, and the payTo wallet from its 402 quote. Only pay if allow is true. If it returns allow: false, tell me the reasons instead of paying. After paying, call report_outcome with the receipt (or the url and payment tx) and short answers about whether you got what you paid for.

3. From code

// Before paying any x402 endpoint, ask Lumière PayCheck.

const res = await fetch("https://lumierepaycheck.org/v1/check-payment", { method: "POST", headers: { "content-type": "application/json" }, body: JSON.stringify({ url: target, amount: quote.amount, payTo: quote.payTo }), }); const decision = await res.json(); if (!decision.allow) throw new Error(Not paying ${target}: ${decision.reasons.join("; ")}); // ...then pay with your x402 client as usual

More in examples/: TypeScript, Python, curl, webhook and receipt verification, a guarded payer, and plan purchase.

API

Free routes allow 60 requests per minute per client, or 300 with a free API key sent in the x-paycheck-key header. The MCP server allows 300 tool calls per minute. Paid routes use x402 with USDC on Base or Solana (same price on both; on Solana the facilitator pays the fee). Lookups for endpoints we don't monitor return 404 and are never charged. Full reference: docs/api.md.

Plans for teams running agents

Free checks stay free. Plans add authorization for agents that spend money:

<img src="assets/5-subscribe.png" alt="Subscribe page: Business trial, setup service, Builder $9/month,