Page speed (one lab measurement)

Load one public URL once in headless Chromium and report what that load measured: navigation timings (TTFB, DOMContentLoaded, load), Web Vitals read from the page's own performance entries (LCP, FCP, CLS, total blocking time from long tasks), total transfer bytes, request count, the 5 heaviest resources, render-blocking scripts and styles, and console errors. Send POST /api/page-speed with the required field url and pay $0.01 per call over x402 or MPP (there is no free tier). It returns a JSON object with url, finalUrl, status, device, viewport and 12 more.

Mobile or desktop viewport. This is a single measurement from one server location under shared load, with no throttling: it is not field data from real users and not a Lighthouse score, and the answer says so in its measurement field. Deterministic code, no model. Body: {"url":"https://…","device":"mobile"|"desktop"?}.

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Parameters

Example request

curl -i -X POST https://agent402.tools/api/page-speed \
  -H "Content-Type: application/json" \
  -d '{"url":"https://agent402.tools","device":"mobile"}'

Without payment this returns HTTP 402 Payment Required with the exact price for page-speed; any x402 v2 or MPP client pays it and retries.

Example response

{
  "url": "https://agent402.tools",
  "finalUrl": "https://agent402.tools/",
  "status": 200,
  "device": "mobile",
  "viewport": {
    "width": 412,
    "height": 823
  },
  "networkIdle": true,
  "timings": {
    "ttfbMs": 182,
    "domContentLoadedMs": 401,
    "loadMs": 655
  },
  "webVitals": {
    "lcpMs": 512,
    "lcpElement": "h1",
    "fcpMs": 430,
    "cls": 0.0012,
    "totalBlockingTimeMs": 0,
    "longTaskCount": 0
  },
  "transfer": {
    "totalBytes": 98123,
    "requestCount": 9,
    "failedRequests": 0
  },
  "heaviestResources": [
    {
      "url": "https://agent402.tools/",
      "type": "document",
      "bytes": 41210
    }
  ],
  "heaviestResourcesPartial": {
    "returned": 1,
    "matched": 9,
    "complete": false,
    "truncated": true
  },
  "renderBlocking": [],
  "renderBlockingPartial": {
    "returned": 0,
    "matched": 0,
    "complete": true,
    "truncated": false
  },
  "consoleErrors": [],
  "consoleErrorsPartial": {
    "returned": 0,
    "matched": 0,
    "complete": true,
    "truncated": false
  },
  "measurement": {
    "kind": "lab-single-run",
    "runs": 1,
    "source": "one load in a headless Chromium from one server location, on shared infrastructure, with no network or CPU throttling",
    "fieldData": false,
    "lighthouseScore": false,
    "note": "A single measurement from one server location under shared load. It is not field data from real users and not a Lighthouse score; repeat the call and compare runs before drawing conclusions."
  },
  "untrustedContent": true
}

From an MCP client

catalog.call {
  "slug": "page-speed",
  "params": {
    "url": "https://agent402.tools",
    "device": "mobile"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for page-speed; the stdio package pays it from a wallet or from an AGENT402_CREDITS_KEY issued earlier. Local install: npx -y agent402-mcp.

Errors and behavior

• url is required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Wallet-only: this tool reaches the network or stored state, so it has no proof-of-work tier. A prepaid card-credits key issued earlier (Authorization: Bearer a402_...) also pays it.
• A GET or HEAD to /api/page-speed returns the same 402 quote, so the price can be read without a body.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

Paid call (JavaScript agent)

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

const client = new x402Client();
client.setSpendControls?.({ maxAmountPerPayment: "$0.01" }); // refuse any quote above this tool's price
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/page-speed", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "url": "https://agent402.tools",
    "device": "mobile"
  }),
});

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