Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add lionkiii/claude-seo-skills --skill seo-core-web-vitalsgit clone --depth 1 https://github.com/lionkiii/claude-seo-skillsWrote 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.
[](https://agentmods.dev/skills/lionkiii/claude-seo-skills/seo-core-web-vitals)<a href="https://agentmods.dev/skills/lionkiii/claude-seo-skills/seo-core-web-vitals"><img src="https://agentmods.dev/badge/skills/lionkiii/claude-seo-skills/seo-core-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.
<a href="https://agentmods.dev/skills/lionkiii/claude-seo-skills/seo-core-web-vitals"><img src="https://agentmods.dev/badge/skills/lionkiii/claude-seo-skills/seo-core-web-vitals.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00099 | $0.02021 |
| Opus 5 | $0.00049 | $0.01010 |
| Sonnet 5 | $0.00020 | $0.00404 |
| Haiku 4.5 | $0.00010 | $0.00202 |
Grade A, and why
seo-core-web-vitals scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl -s -X POST "https://chromeuxreport.googleapis.com/v1/records:queryRecord?key=$CRUX_API_KEY" \ How it starts
The opening of the file, as written. The whole thing — 154 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Core Web Vitals Deep-Dive
Core Web Vitals (CWV) measure real-world loading performance, responsiveness, and visual stability. Google's position, per https://developers.google.com/search/docs/appearance/core-web-vitals: CWV are used by Google's core ranking systems and good CWV is recommended for success with Search — but good scores alone do not guarantee top rankings; there is more to page experience than CWV, and chasing a perfect score purely for SEO is not the best use of time.
INP replaced FID on March 12, 2024. FID is gone from all Chrome tooling. Never reference FID as a current metric.
Thresholds
Each metric is evaluated at the 75th percentile of real page loads, segmented by mobile and desktop. A page "passes" CWV when all three metrics are Good at p75.
| Metric | Measures | Good | Needs Improvement | Poor |
|---|---|---|---|---|
| LCP (Largest Contentful Paint) | Loading | ≤ 2.5s | 2.5s – 4.0s | > 4.0s |
| INP (Interaction to Next Paint) | Responsiveness | ≤ 200ms | 200ms – 500ms | > 500ms |
| CLS (Cumulative Layout Shift) | Visual stability | ≤ 0.1 | 0.1 – 0.25 | > 0.25 |
References: https://web.dev/articles/lcp · https://web.dev/articles/inp · https://web.dev/articles/cls · https://web.dev/articles/vitals
Inputs
| Input | Required | Notes |
|---|---|---|
| URL or origin | Yes | URL-level data preferred; origin-level as fallback |
| Form factor | No | Default: report both mobile (PHONE) and desktop |
| CrUX API key | No | Degrade to PSI API if absent |
Execution
- Field data — CrUX API (preferred, needs an API key):
Docs: https://developer.chrome.com/docs/crux/apicurl -s -X POST "https://chromeuxreport.googleapis.com/v1/records:queryRecord?key=$CRUX_API_KEY" \ -H 'Content-Type: application/json' \ -d '{"url": "<url>", "formFactor": "PHONE", "metrics": ["largest_contentful_paint","interaction_to_next_paint","cumulative_layout_shift"]}'- If the URL has insufficient traffic (404 response), retry with
"origin"instead of"url"and note that results are origin-level. - No API key? Degrade gracefully to step 2 — do not fail.
- If the URL has insufficient traffic (404 response), retry with
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.
- 12d ago First seen · 154 lines · 99 tokens per session scan A b9899840d645
seo-core-web-vitals is a skill published in the GitHub repository lionkiii/claude-seo-skills (20 stars, last pushed 3mo ago), licensed MIT. It adds 99 tokens to every session and 2,021 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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