web-vitals

web-vitals is a skill for Claude Code from prashishh/seo-geo-report-engine. It costs 154 tokens per session (1,173 once invoked), scanned A, original, MIT.

A check of a live web page's Core Web Vitals, which are Google measures of loading speed, responsiveness and visual stability.

In plain words
What is it for?
Use it to check a URL on mobile, desktop or both, review LCP, INP and CLS, and inspect PageSpeed Insights opportunities.
Why use it?
It separates measurements from real Chrome users from results in a controlled Lighthouse test, so you can see how the page performs in practice. It turns the results into a prioritised list of fixes.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is ./bin/mkt 2>/dev/null # (just to resolve a usable python).

Part of the seo-geo-report-engine plugin — 33 skills, 8 commands, 5 agents shipped together

Good fit Use it to check a URL on mobile, desktop or both, review LCP, INP and CLS, and inspect PageSpeed Insights opportunities.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/prashishh/seo-geo-report-engine
agentmods
npx agentmods add skills/prashishh/seo-geo-report-engine/web-vitals

Made for: Claude Code.

Or install seo-geo-report-engine, the plugin that ships this one along with the rest of its 33 skills, 8 commands, 5 agents.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for web-vitals

README.md
[![agentmods](https://agentmods.dev/badge/skills/prashishh/seo-geo-report-engine/web-vitals/github.svg)](https://agentmods.dev/skills/prashishh/seo-geo-report-engine/web-vitals)
Your own site
<a href="https://agentmods.dev/skills/prashishh/seo-geo-report-engine/web-vitals"><img src="https://agentmods.dev/badge/skills/prashishh/seo-geo-report-engine/web-vitals/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for web-vitals

Your own site · 80×15
<a href="https://agentmods.dev/skills/prashishh/seo-geo-report-engine/web-vitals"><img src="https://agentmods.dev/badge/skills/prashishh/seo-geo-report-engine/web-vitals.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 154 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,173 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00154 $0.01173
Opus 5 $0.00077 $0.00587
Sonnet 5 $0.00031 $0.00235
Haiku 4.5 $0.00015 $0.00117

Measured 10d ago against content hash 0a1c27754538, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

web-vitals scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/web-vitals/SKILL.md · 81 lines

How it starts

The opening of the file, as written. The whole thing — 81 lines — stays where its author put it; the contents beside it link to each section on GitHub.

web-vitals

Gets the real, online Core Web Vitals for a live URL and reads them honestly. This is the measurement skill; the optimization methodology lives in core-web-vitals and performance.

Why a separate skill

core-web-vitals and performance describe how to FIX speed. This skill answers "where do we actually stand right now?" using live data from Google's PageSpeed Insights API — both the field (CrUX, real Chrome users, what Google ranks on) and lab (Lighthouse, a single controlled load) numbers. Never report lab numbers as if they were field reality.

Tool

Stdlib, no install. Hits the free PageSpeed Insights API:

./bin/mkt 2>/dev/null  # (just to resolve a usable python)
python3 tools/connectors/pagespeed.py <url>            # mobile
python3 tools/connectors/pagespeed.py <url> desktop
python3 tools/connectors/pagespeed.py <url> both       # mobile + desktop

It returns: performance_score, field_cwv (LCP / INP / CLS / FCP / TTFB with a good / needs-improvement / poor verdict each), field_overall, the lab timings, and the top opportunities. API key: the call works anonymously but is rate-limited (HTTP 429). For repeated use add a free GOOGLE_PSI_API_KEY to config/secrets.env (one click at developers.google.com/speed). The tool retries with backoff and prints a clear message if throttled.

Workflow (PERCEIVE → ANALYZE → VALIDATE → ACT)

  1. PERCEIVE. Run the tool for the target URL, mobile first (Google indexes mobile). Pull both when desktop matters too. If the field block is empty, the URL lacks enough CrUX traffic — say so, and fall back to the lab numbers explicitly labeled as lab-only.

  2. ANALYZE. Grade each Core Web Vital against the thresholds:

    • LCP (loading): good ≤ 2.5s · poor > 4.0s
    • INP (interactivity): good ≤ 200ms · poor > 500ms
    • CLS (visual stability): good ≤ 0.10 · poor > 0.25 Lead with the field verdict (that's the real-user truth and the ranking signal); use lab + opportunities to explain why a failing metric fails. A page can pass field while failing lab, or vice-versa — call that out, don't average them.

Read the full file on GitHub · 81 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 10d ago First seen · 81 lines · 154 tokens per session scan A 0a1c27754538

Subscribe to this mod's changes

web-vitals is a skill published in the GitHub repository prashishh/seo-geo-report-engine (5 stars, last pushed 2mo ago), licensed MIT. It adds 154 tokens to every session and 1,173 once invoked, about $0.0008 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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