Chrome Ux Report MCP server

@pipeworx/chrome-ux-report

Real-user Core Web Vitals for any site with enough traffic, from Google's Chrome UX Report — the 75th-percentile Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift that actual Chrome visitors experienced over the trailing 28 days, plus the distribution behind each number and ~40 weeks of history.

Part of Pipeworx — an MCP gateway connecting AI agents to 1679+ live data sources.

This is the field dataset Google Search uses for its Core Web Vitals assessment, so it answers "is this site passing Core Web Vitals" — which no lab tool, Lighthouse included, can.

Tools

• cruxqueryorigin(origin, form_factor?, metrics?) — the whole site.
• cruxqueryurl(url, form_factor?, metrics?) — one page.
• cruxhistory(origin? | url?, formfactor?, metrics?) — ~40 weekly points.

Auth

BYO with platform fallback: apiKey, or PLATFORMGOOGLEAPIKEY when that secret is set on the gateway. There is no keyless path — the API answers an unkeyed request with HTTP 403 "Method doesn't allow unregistered callers".

A key is free, instant and self-service, with no billing account required: create one at and enable the Chrome UX Report API at . Quota is 150 queries/minute.

The same PLATFORMGOOGLEAPI_KEY serves the pagespeed-insights pack: one Google Cloud key with both APIs enabled covers both.

Data sources

• https://chromeuxreport.googleapis.com/v1/records:queryRecord
• https://chromeuxreport.googleapis.com/v1/records:queryHistoryRecord

Traps, verified live 2026-09-17

PERMISSIONDENIED "Method doesn't allow unregistered callers". Wrong key → HTTP 400 INVALIDARGUMENT "API key not valid". Key whose project has not enabled the API → a third shape (SERVICE_DISABLED). Collapsing them into "auth failed" sends the caller after the wrong problem; each is reported separately.

• The three credential failures look nothing alike. Missing key → HTTP 403

Both together is a 400. An origin must have no path.

• origin and url are different questions and exactly one may be sent.

page or origin once it has enough opted-in Chrome traffic to be statistically sound and non-identifying. That is the dataset's answer, not an outage, and this pack returns it as found: false, reason: "insufficient_traffic". A URL can be absent while its origin is present. Narrower form factors have separate, higher thresholds.

• HTTP 404 is the normal answer for most of the web. CrUX only publishes a

percentile; averaging the histogram gives a different, wrong number.

• The headline number is p75, not the mean. Search assesses at the 75th

as a decimal string while timings are integers. (The PageSpeed Insights API returns the same metric as an integer ×100 — the two Google APIs disagree on the encoding of the same number.)

• CLS is unitless; every other metric is milliseconds. CrUX returns CLS p75

points overlap by 27 days, so a move in the series is a move in a rolling average and a one-week regression shows up damped across four points.

• cruxhistory points are 28-day trailing windows.** Consecutive weekly

Quick Start

Add to your MCP client (Claude Desktop, Cursor, Windsurf, etc.):

{
  "mcpServers": {
    "chrome-ux-report": {
      "url": "https://gateway.pipeworx.io/chrome-ux-report/mcp"
    }
  }
}

What this endpoint actually serves

Shortened. The full README is on GitHub.