[A1] Google CrUX MCP
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[License: MIT]
A1 Google CrUX MCP brings real-user Core Web Vitals data into an AI app. Check whether a public site or page passes LCP, INP and CLS, compare mobile with desktop, and see how the metrics changed over time.
It reads Google’s Chrome UX Report dataset — field data collected from Chrome users, not a synthetic speed test or a way to change your site.
- 6 read-only tools. Core Web Vitals assessment, device comparison, origin-versus-page comparison, 40-week trend and raw latest or historical records.
- Real-user data. It is the same CrUX field data used by PageSpeed Insights and Google’s Core Web Vitals signals.
- Clear availability boundary. Only public origins and URLs with enough real-user traffic have data;
no_data is a valid result.
- Known quota cost. CrUX allows 150 queries per minute per project. Device comparison makes four API calls; origin-versus-page makes two.
Start with a read-only question:
Does https://example.com pass Core Web Vitals on mobile?
Connect the server · Explore use cases · Open technical documentation
See it work in a minute
You: Does https://example.com/pricing pass Core Web Vitals on mobile?
Assistant: Shows p75 LCP, INP and CLS, their good/needs-improvement/poor ratings and the overall result. Nothing changes.
You: Compare this page with the site average and show how mobile differs from desktop.
Assistant: Compares the origin and URL, then device groups and their traffic shares. All six tools read the public CrUX dataset only.
Contents
Quick start
You need Node.js 20+ and a Google Cloud API key with Chrome UX Report API enabled.
- Create a restricted API key.
- Add the server to your AI app.
- Ask the read-only question above.
Codex
In Settings → MCP servers, select Add server, choose STDIO, enter the command npx -y mcp-google-crux@latest and environment variables CRUX_API_KEY, then select Save and Restart.
Codex MCP documentation
Claude Code
Claude Code MCP documentation
Claude Desktop
The current official path is Settings → Extensions. For a custom desktop extension, open Advanced settings → Extension Developer → Install Extension…, select a .mcpb file and follow the prompts.
This repository currently publishes an npm stdio package and does not contain a .mcpb bundle. For Claude Desktop builds that still support local configuration, use the following JSON stdio configuration as a fallback:
{"mcpServers":{"google-crux":{"command":"npx","args":["-y","mcp-google-crux@latest"],"env":{"CRUX_API_KEY":"your_key"}}}}
In those builds, save it to ~/Library/Application Support/Claude/claude_desktop_config.json on macOS or %APPDATA%\Claude\claude_desktop_config.json on Windows.
Claude Desktop MCP documentation
Cursor
Add {"mcpServers":{"google-crux":{"type":"stdio","command":"npx","args":["-y","mcp-google-crux@latest"],"env":{"CRUX_API_KEY":"your_key"}}}} to ~/.cursor/mcp.json on macOS/Linux or %USERPROFILE%\.cursor\mcp.json on Windows. Cursor MCP documentation
VS Code
Run MCP: Open User Configuration and add:
Check it with MCP: List Servers. VS Code MCP documentation
What you can ask it to do
- Does this public origin or URL pass Core Web Vitals?
- Compare phone, desktop, tablet and all-device results.
- Is this page faster or slower than the site average?
- How did LCP, INP and CLS change during the last 25 weeks?
- Show the raw CrUX histograms and percentiles for a technical review.
How to read CrUX data
CrUX reports a rolling 28-day window, updated daily. Historical data is weekly and updates on Mondays. The key value is p75: 75% of observed visits are at or below it. get_core_web_vitals interprets metric thresholds for you; raw record tools expose full histograms and density fractions.
No data does not mean the site is broken. It means Google has no sufficiently large public Chrome-user sample for that origin, URL or device group. Tablets and individual URLs often have no data.
Getting access
- In Google Cloud Console, create or select a project; no billing account is needed for CrUX.
- Enable the Chrome UX Report API.
- Create an API key in APIs & Services → Credentials.
- Restrict the key to Chrome UX Report API and pass it as
CRUX_API_KEY.
The key is stored in the MCP client configuration and is sent in the API request URL, so treat it as a password.
Configuration
Data, limits and background work
- Read-only public dataset. The server cannot alter sites, Search Console, CrUX records or Google rankings.
- Quota-aware retries. It retries
429, 5xx and network errors with backoff. Keep compound comparisons in mind when budgeting the 150 queries per minute project quota.
- No background monitoring. The server works only while called. If your AI app supports scheduled tasks, it can create a recurring performance report.
- Anonymous telemetry. It sends installation and version data plus tool names, never API keys, queried URLs, results, arguments or prompts. For each tool call it also sends the outcome and, on failure, an excerpt of the error text with e-mails, addresses, tokens, numbers of 4+ digits and quoted text replaced by
#; a value from your request can appear in it if the error text contains it. Set ASKADS_TELEMETRY=0 to opt out.
Technical documentation
Support
Found a bug or need a scenario? Create an issue or write in Telegram.
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