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 kostja94/marketing-skills --skill core-web-vitalsgit clone --depth 1 https://github.com/kostja94/marketing-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/kostja94/marketing-skills/core-web-vitals)<a href="https://agentmods.dev/skills/kostja94/marketing-skills/core-web-vitals"><img src="https://agentmods.dev/badge/skills/kostja94/marketing-skills/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/kostja94/marketing-skills/core-web-vitals"><img src="https://agentmods.dev/badge/skills/kostja94/marketing-skills/core-web-vitals.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector pass
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 | $0.01182 |
| Opus 5 | $0.00049 | $0.00591 |
| Sonnet 5 | $0.00020 | $0.00236 |
| Haiku 4.5 | $0.00010 | $0.00118 |
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 9d 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.
Copies of this mod
2 near-identical copies found in the catalogue:
- core-web-vitals — 100% identical, 0 lines differ
- core-web-vitals — 91% identical, 6 lines differ
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:
- Tools: GSC Core Web Vitals report, PageSpeed Insights, Chrome DevTools
- Metrics: Which metric is failing (LCP, INP, CLS)
- 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 |
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.
- 9d ago First seen · 98 lines · 99 tokens per session scan A 7ab585fda04d
core-web-vitals is a skill published in the GitHub repository kostja94/marketing-skills (967 stars, last pushed 3mo 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. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
Other skills, from other repositories
landing-page-generator
Generates high-converting Next.js/React landing pages with Tailwind CSS. Uses PAS, AIDA, and BAB frameworks for optimized copy/components (Heroes, Features, Pricing). Focuses on Core Web Vitals/SEO.
animate
Review a feature and enhance it with purposeful animations, micro-interactions, and motion effects that improve usability and delight. Use when the user mentions adding animation, transitions, micro-interactions, motion design, hover effects, or making the UI feel more alive.
audit
Run technical quality checks across accessibility, performance, theming, responsive design, and anti-patterns. Generates a scored report with P0-P3 severity ratings and actionable plan. Use when the user wants an accessibility check, performance audit, or technical quality review.
adapt
Adapt designs to work across different screen sizes, devices, contexts, or platforms. Implements breakpoints, fluid layouts, and touch targets. Use when the user mentions responsive design, mobile layouts, breakpoints, viewport adaptation, or cross-device compatibility.
saas-landing
A single-page SaaS landing page for a software product, with sections such as the hero, features, customer proof, pricing, FAQs, and a call to action. SaaS means software delivered online, usually by subscription.
Dark Mode Bug Finder
Detect dark mode rendering issues including contrast failures, missing theme tokens, image inversions, and transition glitches across components.