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Corewebvitals WebMCP tools

Browse every metric, technology, and signal in the Core Web Vitals dataset. Real-user data from 189,915 sites.

3 tools1 ways to use

What an agent can do on Corewebvitals

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: what it does, how to install it, and the input fields an agent should send.

WebMCP tools on Corewebvitals

Search & find

get_metrics

Read the full get_metrics page

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_metrics

Install 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

metrics string 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.
filter object Optional AND filters. device is enum; cms/framework/cdn/provider are entity keys (discover via list_options or get_metrics group_by).
group_by string Rank by this dimension: one row per entity (e.g. group_by=cms for CMS standings). Omit for a single aggregate row.
limit number Max groups when group_by is set. Default 25.
min_sites number Drop groups with fewer than this many sites. Default 50.
focus string When correlating techniques with CWV, which CWV to focus on. Default lcp.

Open the source definition

Get data

get_histogram

Read the full get_histogram page

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_histogram

Install 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

metric string Primary: lcp | inp | cls | fcp | ttfb. May also be a scalar technique contract path.
filter object Optional AND filters. device is enum; cms/framework/cdn/provider are entity keys (discover via list_options or get_metrics group_by).

Open the source definition

Search & find

list_options

Read the full list_options page

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_options

Install 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

kind string Subset to return. Omit or "all" for the full discovery payload.
include_paths boolean If true, include technique contract path samples when available.

Open the source definition