webperf-core-web-vitals

1# WebPerf: Core Web Vitals
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3JavaScript snippets for measuring web performance in Chrome DevTools.
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5## Running a script
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71. Run the script with `mcp__chrome-devtools__evaluate_script`, passing the file instead of its code: `sourcePath` with the absolute path of `scripts/<Name>.js` in this skill, and `format: "script"`, since a script runs by itself and is not a function. Read the object it returns. The scripts have no console output, so the returned object is the result: `script`, `status` and the metric data (`value`, `rating`, `details`, `items`, `issues`), as described in `references/schema.md`.
82. When `status` is `"tracking"`, the script keeps observing the page. After the interactions, call the function named in `getDataFn` with another `mcp__chrome-devtools__evaluate_script` call, as an arrow function in `function`, for example `() => getINP()`, and read the object it returns.
93. When `status` is `"error"` or `"unsupported"`, read `error`: the page may not have loaded yet, or the browser lacks the API.
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