Core Web Vitals optimization workflow skill. Use this skill when the user needs Optimize Core Web Vitals (LCP, INP, CLS) for better page experience and search ranking. Use when asked to "improve Core Web Vitals", "fix LCP", "reduce CLS", "optimize INP", "page experience optimization", or "fix layout shifts". Focuses specifically on the three Core Web Vitals metrics. Do NOT use for general web performance (use perf-web-optimization), Lighthouse audits (use perf-lighthouse), or Astro-specific optimization (use perf-astro) and the operator should preserve the upstream workflow, copied support files, and provenance before merging or handing off.
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SKILL.md
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name
core-web-vitals
description
Core Web Vitals optimization workflow skill. Use this skill when the user needs Optimize Core Web Vitals (LCP, INP, CLS) for better page experience and search ranking. Use when asked to "improve Core Web Vitals", "fix LCP", "reduce CLS", "optimize INP", "page experience optimization", or "fix layout shifts". Focuses specifically on the three Core Web Vitals metrics. Do NOT use for general web performance (use perf-web-optimization), Lighthouse audits (use perf-lighthouse), or Astro-specific optimization (use perf-astro) and the operator should preserve the upstream workflow, copied support files, and provenance before merging or handing off.
This public intake copy packages packages/skills-catalog/skills/(performance)/core-web-vitals from https://github.com/tech-leads-club/agent-skills into the native Omni Skills editorial shape without hiding its origin.
Use it when the operator needs the upstream workflow, support files, and repository context to stay intact while the public validator and private enhancer continue their normal downstream flow.
This intake keeps the copied upstream files intact and uses the external_source block in metadata.json plus ORIGIN.md as the provenance anchor for review.
Core Web Vitals optimization Targeted optimization for the three Core Web Vitals metrics that affect Google Search ranking and user experience.
Imported source sections that did not map cleanly to the public headings are still preserved below or in the support files. Notable imported sections: The three metrics, LCP: Largest Contentful Paint, INP: Interaction to Next Paint, CLS: Cumulative Layout Shift, Measurement tools, Framework quick fixes.
When to Use This Skill
Use this section as the trigger filter. It should make the activation boundary explicit before the operator loads files, runs commands, or opens a pull request.
Use when the request clearly matches the imported source intent: Optimize Core Web Vitals (LCP, INP, CLS) for better page experience and search ranking. Use when asked to "improve Core Web Vitals", "fix LCP", "reduce CLS", "optimize INP", "page experience optimization", or "fix....
Use when the operator should preserve upstream workflow detail instead of rewriting the process from scratch.
Use when provenance needs to stay visible in the answer, PR, or review packet.
Use when copied upstream references, examples, or scripts materially improve the answer.
Use when the workflow should remain reviewable in the public intake repo before the private enhancer takes over.
Operating Table
Situation
Start here
Why it matters
First-time use
metadata.json
Confirms repository, branch, commit, and imported path through the external_source block before touching the copied workflow
Provenance review
ORIGIN.md
Gives reviewers a plain-language audit trail for the imported source
Workflow execution
references/LCP.md
Starts with the smallest copied file that materially changes execution
Supporting context
references/LCP.md
Adds the next most relevant copied source file without loading the entire package
Handoff decision
## Related Skills
Helps the operator switch to a stronger native skill when the task drifts
Workflow
This workflow is intentionally editorial and operational at the same time. It keeps the imported source useful to the operator while still satisfying the public intake standards that feed the downstream enhancer flow.
Confirm the user goal, the scope of the imported workflow, and whether this skill is still the right router for the task.
Read the overview and provenance files before loading any copied upstream support files.
Load only the references, examples, prompts, or scripts that materially change the outcome for the current request.
Execute the upstream workflow while keeping provenance and source boundaries explicit in the working notes.
Validate the result against the upstream expectations and the evidence you can point to in the copied files.
Escalate or hand off to a related skill when the work moves out of this imported workflow's center of gravity.
Before merge or closure, record what was used, what changed, and what the reviewer still needs to verify.
Imported Workflow Notes
Imported: The three metrics
Metric
Measures
Good
Needs work
Poor
LCP
Loading
≤ 2.5s
2.5s – 4s
> 4s
INP
Interactivity
≤ 200ms
200ms – 500ms
> 500ms
CLS
Visual Stability
≤ 0.1
0.1 – 0.25
> 0.25
Google measures at the 75th percentile — 75% of page visits must meet "Good" thresholds.
Examples
Example 1: Ask for the upstream workflow directly
Use @core-web-vitals to handle <task>. Start from the copied upstream workflow, load only the files that change the outcome, and keep provenance visible in the answer.
Explanation: This is the safest starting point when the operator needs the imported workflow, but not the entire repository.
Example 2: Ask for a provenance-grounded review
Review @core-web-vitals against metadata.json and ORIGIN.md, then explain which copied upstream files you would load first and why.
Explanation: Use this before review or troubleshooting when you need a precise, auditable explanation of origin and file selection.
Example 3: Narrow the copied support files before execution
Use @core-web-vitals for <task>. Load only the copied references, examples, or scripts that change the outcome, and name the files explicitly before proceeding.
Explanation: This keeps the skill aligned with progressive disclosure instead of loading the whole copied package by default.
Example 4: Build a reviewer packet
Review @core-web-vitals using the copied upstream files plus provenance, then summarize any gaps before merge.
Explanation: This is useful when the PR is waiting for human review and you want a repeatable audit packet.
Best Practices
Treat the generated public skill as a reviewable packaging layer around the upstream repository. The goal is to keep provenance explicit and load only the copied source material that materially improves execution.
Keep the imported skill grounded in the upstream repository; do not invent steps that the source material cannot support.
Prefer the smallest useful set of support files so the workflow stays auditable and fast to review.
Keep provenance, source commit, and imported file paths visible in notes and PR descriptions.
Point directly at the copied upstream files that justify the workflow instead of relying on generic review boilerplate.
Treat generated examples as scaffolding; adapt them to the concrete task before execution.
Route to a stronger native skill when architecture, debugging, design, or security concerns become dominant.
Troubleshooting
Problem: The operator skipped the imported context and answered too generically
Symptoms: The result ignores the upstream workflow in packages/skills-catalog/skills/(performance)/core-web-vitals, fails to mention provenance, or does not use any copied source files at all.
Solution: Re-open metadata.json, ORIGIN.md, and the most relevant copied upstream files. Check the external_source block first, then restate the provenance before continuing.
Problem: The imported workflow feels incomplete during review
Symptoms: Reviewers can see the generated SKILL.md, but they cannot quickly tell which references, examples, or scripts matter for the current task.
Solution: Point at the exact copied references, examples, scripts, or assets that justify the path you took. If the gap is still real, record it in the PR instead of hiding it.
Problem: The task drifted into a different specialization
Symptoms: The imported skill starts in the right place, but the work turns into debugging, architecture, design, security, or release orchestration that a native skill handles better.
Solution: Use the related skills section to hand off deliberately. Keep the imported provenance visible so the next skill inherits the right context instead of starting blind.
Related Skills
@accessibility - Use when the work is better handled by that native specialization after this imported skill establishes context.
@ai-cold-outreach - Use when the work is better handled by that native specialization after this imported skill establishes context.
@ai-pricing - Use when the work is better handled by that native specialization after this imported skill establishes context.
@ai-sdr - Use when the work is better handled by that native specialization after this imported skill establishes context.
Additional Resources
Use this support matrix and the linked files below as the operator packet for this imported skill. They should reflect real copied source material, not generic scaffolding.
Resource family
What it gives the reviewer
Example path
references
copied reference notes, guides, or background material from upstream
references/LCP.md
examples
worked examples or reusable prompts copied from upstream
examples/n/a
scripts
upstream helper scripts that change execution or validation
scripts/n/a
agents
routing or delegation notes that are genuinely part of the imported package
agents/n/a
assets
supporting assets or schemas copied from the source package
<!-- ❌ No hints, discovered late --><imgsrc="/hero.jpg"alt="Hero" /><!-- ✅ Preloaded with high priority --><linkrel="preload"href="/hero.webp"as="image"fetchpriority="high" /><imgsrc="/hero.webp"alt="Hero"fetchpriority="high" />
4. Client-side rendering delays
// ❌ Content loads after JavaScriptuseEffect(() => {
fetch('/api/hero-text')
.then((r) => r.json())
.then(setHeroText)
}, [])
// ✅ Server-side or static rendering// Use SSR, SSG, or streaming to send HTML with contentexportasyncfunctiongetServerSideProps() {
const heroText = awaitfetchHeroText()
return { props: { heroText } }
}
LCP optimization checklist
- [ ] TTFB < 800ms (use CDN, edge caching)
- [ ] LCP image preloaded with fetchpriority="high"
- [ ] LCP image optimized (WebP/AVIF, correct size)
- [ ] Critical CSS inlined (< 14KB)
- [ ] No render-blocking JavaScript in <head>- [ ] Fonts don't block text rendering (font-display: swap)
- [ ] LCP element in initial HTML (not JS-rendered)
INP measures responsiveness across ALL interactions (clicks, taps, key presses) during a page visit. It reports the worst interaction (at 98th percentile for high-traffic pages).
INP breakdown
Total INP = Input Delay + Processing Time + Presentation Delay
Phase
Target
Optimization
Input Delay
< 50ms
Reduce main thread blocking
Processing
< 100ms
Optimize event handlers
Presentation
< 50ms
Minimize rendering work
Common INP issues
1. Long tasks blocking main thread
// ❌ Long synchronous taskfunctionprocessLargeArray(items) {
items.forEach((item) =>expensiveOperation(item))
}
// ✅ Break into chunks with yieldingasyncfunctionprocessLargeArray(items) {
constCHUNK_SIZE = 100for (let i = 0; i < items.length; i += CHUNK_SIZE) {
const chunk = items.slice(i, i + CHUNK_SIZE)
chunk.forEach((item) =>expensiveOperation(item))
// Yield to main threadawaitnewPromise((r) =>setTimeout(r, 0))
// Or use scheduler.yield() when available
}
}
2. Heavy event handlers
// ❌ All work in handler
button.addEventListener('click', () => {
// Heavy computationconst result = calculateComplexThing()
// DOM updatesupdateUI(result)
// AnalyticstrackEvent('click')
})
// ✅ Prioritize visual feedback
button.addEventListener('click', () => {
// Immediate visual feedback
button.classList.add('loading')
// Defer non-critical workrequestAnimationFrame(() => {
const result = calculateComplexThing()
updateUI(result)
})
// Use requestIdleCallback for analyticsrequestIdleCallback(() =>trackEvent('click'))
})
CLS measures unexpected layout shifts. A shift occurs when a visible element changes position between frames without user interaction.
CLS Formula:impact fraction × distance fraction
Common CLS causes
1. Images without dimensions
<!-- ❌ Causes layout shift when loaded --><imgsrc="photo.jpg"alt="Photo" /><!-- ✅ Space reserved --><imgsrc="photo.jpg"alt="Photo"width="800"height="600" /><!-- ✅ Or use aspect-ratio --><imgsrc="photo.jpg"alt="Photo"style="aspect-ratio: 4/3; width: 100%;" />
2. Ads, embeds, and iframes
<!-- ❌ Unknown size until loaded --><iframesrc="https://ad-network.com/ad"></iframe><!-- ✅ Reserve space with min-height --><divstyle="min-height: 250px;"><iframesrc="https://ad-network.com/ad"height="250"></iframe></div><!-- ✅ Or use aspect-ratio container --><divstyle="aspect-ratio: 16/9;"><iframesrc="https://youtube.com/embed/..."style="width: 100%; height: 100%;"></iframe></div>
- [ ] All images have width/height or aspect-ratio
- [ ] All videos/embeds have reserved space
- [ ] Ads have min-height containers
- [ ] Fonts use font-display: optional or matched metrics
- [ ] Dynamic content inserted below viewport
- [ ] Animations use transform/opacity only
- [ ] No content injected above existing content
