---
name: seo-core-web-vitals
description: "Core Web Vitals analyzer for LCP, FID, CLS, INP performance metrics. Triggers: Core Web Vitals, page speed, LCP, CLS, FID, INP, performance."
allowed-tools: mcp__firecrawl__*, mcp__perplexity__*
---

# SEO Core Web Vitals

## Purpose

Analyze Core Web Vitals performance metrics and provide optimization recommendations.

## Core Capabilities

1. **LCP** - Largest Contentful Paint measurement
2. **FID/INP** - Interactivity metrics
3. **CLS** - Cumulative Layout Shift
4. **Recommendations** - Optimization guidance

## Metrics Thresholds

| Metric | Good | Needs Work | Poor |
|--------|------|------------|------|
| LCP | ≤2.5s | 2.5-4s | >4s |
| FID | ≤100ms | 100-300ms | >300ms |
| CLS | ≤0.1 | 0.1-0.25 | >0.25 |
| INP | ≤200ms | 200-500ms | >500ms |

## Data Sources

### Option 1: PageSpeed Insights (Recommended)
Use external tool and input results:
- Visit: https://pagespeed.web.dev/
- Enter URL, run test
- Provide scores to skill

### Option 2: Research Best Practices
```
mcp__perplexity__search: "Core Web Vitals optimization [specific issue]"
```

## Workflow

1. Request PageSpeed Insights data from user
2. Analyze provided metrics
3. Identify failing metrics
4. Research optimization strategies
5. Provide prioritized recommendations

## Common LCP Issues

| Cause | Fix |
|-------|-----|
| Slow server response | Improve TTFB, use CDN |
| Render-blocking resources | Defer non-critical CSS/JS |
| Slow resource load | Preload LCP image |
| Client-side rendering | Use SSR/SSG |

## Common CLS Issues

| Cause | Fix |
|-------|-----|
| Images without dimensions | Add width/height attributes |
| Ads/embeds without space | Reserve space with CSS |
| Web fonts causing FOIT/FOUT | Use font-display: swap |
| Dynamic content injection | Reserve space, use transforms |

## Common INP Issues

| Cause | Fix |
|-------|-----|
| Long JavaScript tasks | Break up tasks, use web workers |
| Large DOM size | Reduce DOM nodes |
| Heavy event handlers | Debounce, optimize listeners |
| Third-party scripts | Defer, lazy load |

## Output Format

```markdown
## Core Web Vitals: [URL]

### Scores
| Metric | Mobile | Desktop | Status |
|--------|--------|---------|--------|
| LCP | Xs | Xs | Good/Poor |
| FID | Xms | Xms | Good/Poor |
| CLS | X.XX | X.XX | Good/Poor |
| INP | Xms | Xms | Good/Poor |

### Overall Score
- Mobile: X/100
- Desktop: X/100

### Priority Fixes
1. [Highest impact recommendation]
2. [Second priority]

### Detailed Recommendations
[Per-metric optimization steps]
```

## Limitations

- Requires external PageSpeed Insights data
- Lab data may differ from field data
- Some fixes require developer implementation
- Third-party scripts may be difficult to optimize

## Notion Output (Required)

All audit reports MUST be saved to OurDigital SEO Audit Log:
- **Database ID**: `2c8581e5-8a1e-8035-880b-e38cefc2f3ef`
- **Properties**: Issue (title), Site (url), Category, Priority, Found Date, Audit ID
- **Language**: Korean with English technical terms
- **Audit ID Format**: [TYPE]-YYYYMMDD-NNN