core-web-vitals

core-web-vitals is a skill for Claude Code, Codex from T4wroot/agentic-seo. It costs 99 tokens per session (1,182 once invoked), scanned A, a copy of core-web-vitals, MIT.

A guide to Core Web Vitals, Google's measures of page loading speed, responsiveness, and visual stability. It covers LCP, INP, and CLS.

In plain words
What is it for?
Use it to assess and improve slow loading, delayed interactions, and unexpected layout movement on websites.
Why use it?
It helps identify page-performance problems that can hurt user experience and search visibility.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to assess and improve slow loading, delayed interactions, and unexpected layout movement on websites.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/t4wroot/agentic-seo/core-web-vitals
Install

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.

Any agent
npx skills add T4wroot/agentic-seo --skill core-web-vitals
Clone the repo
git clone --depth 1 https://github.com/T4wroot/agentic-seo

Made for: Claude Code, Codex.

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 core-web-vitals

README.md
[![agentmods](https://agentmods.dev/badge/skills/t4wroot/agentic-seo/core-web-vitals/github.svg)](https://agentmods.dev/skills/t4wroot/agentic-seo/core-web-vitals)
Your own site
<a href="https://agentmods.dev/skills/t4wroot/agentic-seo/core-web-vitals"><img src="https://agentmods.dev/badge/skills/t4wroot/agentic-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.

agentmods 80×15 button for core-web-vitals

Your own site · 80×15
<a href="https://agentmods.dev/skills/t4wroot/agentic-seo/core-web-vitals"><img src="https://agentmods.dev/badge/skills/t4wroot/agentic-seo/core-web-vitals.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 99 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,182 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 100% copy Near-identical to another mod 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 $0.00099 $0.01182
Opus 5 $0.00049 $0.00591
Sonnet 5 $0.00020 $0.00236
Haiku 4.5 $0.00010 $0.00118

Measured 8d ago against content hash 7ab585fda04d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

core-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 8d 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.

Origin

This is a copy

100% identical to core-web-vitals — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/seo/technical/core-web-vitals/SKILL.md · 98 lines

How it starts

The opening of the file, as written. The whole thing — 98 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SEO Technical: Core Web Vitals

Guides optimization of Core Web Vitals (CWV)—Google's user experience metrics that affect search ranking. CWV are confirmed ranking factors for mobile and desktop.

When invoking: On first use, if helpful, open with 1–2 sentences on what this skill covers and why it matters, then provide the main output. On subsequent use or when the user asks to skip, go directly to the main output.

Scope (Technical SEO)

  • LCP (Largest Contentful Paint): Loading performance; time to render largest content element
  • INP (Interaction to Next Paint): Responsiveness; replaced FID on March 12, 2024
  • CLS (Cumulative Layout Shift): Visual stability; unexpected layout shifts

Target Thresholds (75th percentile, field data)

Metric Target Good Needs Improvement Poor
LCP ≤2.5s ≤2.5s 2.5–4.0s >4.0s
INP ≤200ms ≤200ms 200–500ms >500ms
CLS <0.1 ≤0.1 0.1–0.25 >0.25

Source: Google Page Experience

Initial Assessment

Check for project context first: If .claude/project-context.md or .cursor/project-context.md exists, read it for site URL.

Identify:

  1. Tools: GSC Core Web Vitals report, PageSpeed Insights, Chrome DevTools
  2. Metrics: Which metric is failing (LCP, INP, CLS)
  3. Page type: Hero, article, product, list—LCP candidate differs

LCP Optimization

LCP measures the time until the largest content element (image, video, or text block) is visible.

Cause Fix
Slow server response Reduce TTFB; use CDN; optimize server
Render-blocking resources Defer non-critical CSS/JS; inline critical CSS
Large images WebP/AVIF; compress; width/height to prevent CLS; see image-optimization
Client-side rendering SSR/SSG for above-fold content; see rendering-strategies
Third-party scripts Load async; defer non-critical

Read the full file on GitHub · 98 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. 8d ago First seen · 98 lines · 99 tokens per session scan A 7ab585fda04d

Subscribe to this mod's changes

core-web-vitals is a skill published in the GitHub repository T4wroot/agentic-seo (15 stars, last pushed 9d ago), licensed MIT. It adds 99 tokens to every session and 1,182 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to core-web-vitals, differing in 0 lines, and is treated as a copy.

Related

Other skills, from other repositories

fire-your-seo-agency

A procedure for improving how a website appears in search engines and how AI answer systems find and cite it. It covers search, answer-engine, generative-AI, and Naver visibility.

leopard627/fire-your-seo-agency · 162 tokens

improve-aeo-geo

Audits a website codebase and makes code changes so AI engines (ChatGPT, Claude, Perplexity, Google AI Overviews) can better discover, parse, quote, and cite the site. Covers structured data, content structure, technical signals, and freshness.

onvoyage-ai/gtm-engineer-skills · 61 tokens

build-resource-pages

Takes existing content markdown files and builds production-final resource center pages on client websites using their existing tech stack and design system. Output is live-ready — no review pass, no placeholder content, no prototype styling. Implements hub pages, section listings, article pages, and cross-linking for…

onvoyage-ai/gtm-engineer-skills · 72 tokens

seo-ai-site-builders

Turn a JavaScript-only site built by an AI website generator into indexable HTML. Input: a site made with Lovable, Base44, Bolt, v0, Replit, Firebase Studio, Framer, Wix, Durable, Softr, Bubble, Glide or any similar tool. Output: proof of what crawlers actually receive (bundled zero-dependency script), the right…

Thibaultbm/claude-seo-geo · 183 tokens

content-thicken

Evidence-driven blog driver. Takes ONE target from the fused search plus AI-answer content library, pulls the real questions it has to answer, drafts a thick long-form guide against a template contract, validates it deterministically, and stops at preview. Two modes, thicken an already-earning post IN PLACE (never…

Jasper0122/agent-seo-kit · 126 tokens

backlink-outreach

Find, evaluate, pitch and track natural backlink and content partnerships. Prospects come from the GEO citation data rather than a generic blog search: the targets are the pages an AI already cites when answering your category questions. Research runs on the Monid tool layer (web search and scrape, authority metrics…

Jasper0122/agent-seo-kit · 133 tokens