@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

• crux_query_origin(origin, form_factor?, metrics?) — the whole site.

• crux_query_url(url, form_factor?, metrics?) — one page.

• crux_history(origin? | url?, form_factor?, metrics?) — ~40 weekly points.

Related MCP server: State of Web Vitals MCP

Auth

BYO with platform fallback: _apiKey, or PLATFORM_GOOGLE_API_KEY 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 https://console.cloud.google.com/apis/credentials and enable the Chrome UX Report API at https://console.cloud.google.com/apis/library/chromeuxreport.googleapis.com. Quota is 150 queries/minute.

The same PLATFORM_GOOGLE_API_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

• The three credential failures look nothing alike. Missing key → HTTP 403 PERMISSION_DENIED "Method doesn't allow unregistered callers". Wrong key → HTTP 400 INVALID_ARGUMENT "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.

• origin and url are different questions and exactly one may be sent. Both together is a 400. An origin must have no path.

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

• The headline number is p75, not the mean. Search assesses at the 75th percentile; averaging the histogram gives a different, wrong number.

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

• crux_history points are 28-day trailing windows. Consecutive weekly 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.

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

tools/list at https://gateway.pipeworx.io/chrome-ux-report/mcp returns the tools in the table above plus the shared Pipeworx meta-tools — ask_pipeworx, discover_tools, search_within, remember/recall and the rest of the gateway-wide set. So the tool count you see is larger than this table: a single-pack endpoint currently lists roughly 30 shared tools alongside the pack's own. The connection's initialize response states its exact scope, and is the authoritative answer for a given day.

This is deliberate, not multiplexing by accident. The meta-tools are what let a scoped connection answer a question this pack does not cover — via ask_pipeworx, which routes across the whole catalog — without you adding a second MCP server. There is currently no way to mount a pack endpoint without them; if the extra schemas cost you more context than the routing is worth, connect to the full gateway once rather than to several pack endpoints.

Or connect to the full Pipeworx gateway to get every pack's tools listed directly, instead of just this one's:

{
  "mcpServers": {
    "pipeworx": {
      "url": "https://gateway.pipeworx.io/mcp"
    }
  }
}

Both URLs reach the same gateway and the same 1679+ data sources. The only difference is which pack's tools are listed directly; ask_pipeworx reaches all of them from either one.

No MCP client? Call it over HTTP

curl -X POST https://gateway.pipeworx.io/v1/tools/crux_query_origin \
  -H 'Content-Type: application/json' \
  -d '{"origin":"https://www.shopify.com"}'

No account needed for the first calls. Inspect any tool: GET https://gateway.pipeworx.io/v1/tools/crux_query_origin. Find one: POST https://gateway.pipeworx.io/v1/tools/search_packs with {"query":"..."}.

Standalone (no gateway account)

This package also runs as a local stdio MCP server — no Pipeworx account, no gateway round-trip:

{
  "mcpServers": {
    "chrome-ux-report": {
      "command": "npx",
      "args": ["-y", "@pipeworx/mcp-chrome-ux-report"]
    }
  }
}

Or run it directly to confirm it starts:

npx -y @pipeworx/mcp-chrome-ux-report

It speaks MCP over stdin/stdout and answers initialize/tools/list/tools/call for only this pack's tools — none of the shared meta-tools the gateway connection above adds. Same source, same tools, no ask_pipeworx routing.

Using with ask_pipeworx

Instead of calling tools directly, you can ask questions in plain English — this works on the pack endpoint above as well as on the full gateway:

ask_pipeworx({ question: "your question about Chrome Ux Report data" })

The gateway picks the right tool and fills the arguments automatically.

More

• Docs and guides

• pipeworx.io

License

MIT