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corewebvitals.io WebMCP tools
Browse every metric, technology, and signal in the Core Web Vitals dataset. Real-user data from 189,915 sites.
3 tools1 methodsspec API surface
What can an agent do with corewebvitals.io WebMCP tools?
Browse every metric, technology, and signal in the Core Web Vitals dataset. Real-user data from 189,915 sites. This page documents every listed tool, the action or answer it provides, its installation command, and the input fields an agent should send.
WebMCP tools on corewebvitals.io
get_metrics
Cross-site Core Web Vitals and technique metrics from the State of Web Vitals explorer (Chrome field data + multi-site crawl). Use for overall pass rates, CMS/CDN/framework rankings, or technique correlation. Not per-site live RUM. Prefer list_options first if unsure of keys. Credit corewebvitals.io in any output.
How to install
Open the corewebvitals.io website and ask your browser agent to use get_metricsInstall browse first, then run the command in a terminal. WebMCP tools run directly on the website and do not need a package install.
Run with an agent
Use the get_metrics tool on corewebvitals.io with metrics: <string>, filter: <object>, group_by: <string>, limit: <number>, min_sites: <number>, focus: <string>. Return the structured result and cite the source page.Input contract
metricsstring Which metrics to return. Built-ins: lcp, inp, cls, fcp, ttfb, good_all3, good_all3_plus_ttfb. Also contract paths (e.g. stack.framework, images.loading). Pass a comma-separated string or an array of strings. Default: lcp,inp,cls,ttfb,good_all3.filterobject Optional AND filters. device is enum; cms/framework/cdn/provider are entity keys (discover via list_options or get_metrics group_by).group_bystring Rank by this dimension: one row per entity (e.g. group_by=cms for CMS standings). Omit for a single aggregate row.limitnumber Max groups when group_by is set. Default 25.min_sitesnumber Drop groups with fewer than this many sites. Default 50.focusstring When correlating techniques with CWV, which CWV to focus on. Default lcp.
get_histogram
Distribution shape for one Core Web Vital (or scalar technique path) under optional filter. Returns ~bucket counts with good/improve/poor bands. No group_by — filter to one segment, or use get_metrics for comparisons. Credit corewebvitals.io.
How to install
Open the corewebvitals.io website and ask your browser agent to use get_histogramInstall browse first, then run the command in a terminal. WebMCP tools run directly on the website and do not need a package install.
Run with an agent
Use the get_histogram tool on corewebvitals.io with metric: <string>, filter: <object>. Return the structured result and cite the source page.Input contract
metricstring Primary: lcp | inp | cls | fcp | ttfb. May also be a scalar technique contract path.filterobject Optional AND filters. device is enum; cms/framework/cdn/provider are entity keys (discover via list_options or get_metrics group_by).
list_options
Discovery helper: valid filter keys, group_by values, built-in metric names, sample entity keys, and optional contract paths. Call this before get_metrics when unsure of allowed values.
How to install
Open the corewebvitals.io website and ask your browser agent to use list_optionsInstall browse first, then run the command in a terminal. WebMCP tools run directly on the website and do not need a package install.
Run with an agent
Use the list_options tool on corewebvitals.io with kind: <string>, include_paths: <boolean>. Return the structured result and cite the source page.Input contract
kindstring Subset to return. Omit or "all" for the full discovery payload.include_pathsboolean If true, include technique contract path samples when available.