#363

Global Rank · of 600 Skills

web-perf AI Agent Skill

View Source: cloudflare/skills

Medium

Installation

npx skills add cloudflare/skills --skill web-perf

5.6K

Installs

Web Performance Audit

Your knowledge of web performance metrics, thresholds, and tooling APIs may be outdated. Prefer retrieval over pre-training when citing specific numbers or recommendations.

Retrieval Sources

Source	How to retrieve	Use for
web.dev	`https://web.dev/articles/vitals`	Core Web Vitals thresholds, definitions
Chrome DevTools docs	`https://developer.chrome.com/docs/devtools/performance`	Tooling APIs, trace analysis
Lighthouse scoring	`https://developer.chrome.com/docs/lighthouse/performance/performance-scoring`	Score weights, metric thresholds

FIRST: Verify MCP Tools Available

Run this before starting. Try calling navigate_page or performance_start_trace. If unavailable, STOP—the chrome-devtools MCP server isn't configured.

Ask the user to add this to their MCP config:

"chrome-devtools": {
  "type": "local",
  "command": ["npx", "-y", "chrome-devtools-mcp@latest"]
}

Key Guidelines

Be assertive: Verify claims by checking network requests, DOM, or codebase—then state findings definitively.
Verify before recommending: Confirm something is unused before suggesting removal.
Quantify impact: Use estimated savings from insights. Don't prioritize changes with 0ms impact.
Skip non-issues: If render-blocking resources have 0ms estimated impact, note but don't recommend action.
Be specific: Say "compress hero.png (450KB) to WebP" not "optimize images".
Prioritize ruthlessly: A site with 200ms LCP and 0 CLS is already excellent—say so.

Quick Reference

Task	Tool Call
Load page	`navigate_page(url: "...")`
Start trace	`performance_start_trace(autoStop: true, reload: true)`
Analyze insight	`performance_analyze_insight(insightSetId: "...", insightName: "...")`
List requests	`list_network_requests(resourceTypes: ["Script", "Stylesheet", ...])`
Request details	`get_network_request(reqid: <id>)`
A11y snapshot	`take_snapshot(verbose: true)`

Workflow

Copy this checklist to track progress:

Audit Progress:
- [ ] Phase 1: Performance trace (navigate + record)
- [ ] Phase 2: Core Web Vitals analysis (includes CLS culprits)
- [ ] Phase 3: Network analysis
- [ ] Phase 4: Accessibility snapshot
- [ ] Phase 5: Codebase analysis (skip if third-party site)

Phase 1: Performance Trace

Navigate to the target URL:
```
navigate_page(url: "<target-url>")
```
Start a performance trace with reload to capture cold-load metrics:
```
performance_start_trace(autoStop: true, reload: true)
```
Wait for trace completion, then retrieve results.

Troubleshooting:

If trace returns empty or fails, verify the page loaded correctly with navigate_page first
If insight names don't match, inspect the trace response to list available insights

Phase 2: Core Web Vitals Analysis

Use performance_analyze_insight to extract key metrics.

Note: Insight names may vary across Chrome DevTools versions. If an insight name doesn't work, check the insightSetId from the trace response to discover available insights.

Common insight names:

Metric	Insight Name	What to Look For
LCP	`LCPBreakdown`	Time to largest contentful paint; breakdown of TTFB, resource load, render delay
CLS	`CLSCulprits`	Elements causing layout shifts (images without dimensions, injected content, font swaps)
Render Blocking	`RenderBlocking`	CSS/JS blocking first paint
Document Latency	`DocumentLatency`	Server response time issues
Network Dependencies	`NetworkRequestsDepGraph`	Request chains delaying critical resources

Example:

performance_analyze_insight(insightSetId: "<id-from-trace>", insightName: "LCPBreakdown")

Key thresholds (good/needs-improvement/poor):

TTFB: < 800ms / < 1.8s / > 1.8s
FCP: < 1.8s / < 3s / > 3s
LCP: < 2.5s / < 4s / > 4s
INP: < 200ms / < 500ms / > 500ms
TBT: < 200ms / < 600ms / > 600ms
CLS: < 0.1 / < 0.25 / > 0.25
Speed Index: < 3.4s / < 5.8s / > 5.8s

Phase 3: Network Analysis

List all network requests to identify optimization opportunities:

list_network_requests(resourceTypes: ["Script", "Stylesheet", "Document", "Font", "Image"])

Look for:

Render-blocking resources: JS/CSS in <head> without async/defer/media attributes
Network chains: Resources discovered late because they depend on other resources loading first (e.g., CSS imports, JS-loaded fonts)
Missing preloads: Critical resources (fonts, hero images, key scripts) not preloaded
Caching issues: Missing or weak Cache-Control, ETag, or Last-Modified headers
Large payloads: Uncompressed or oversized JS/CSS bundles
Unused preconnects: If flagged, verify by checking if ANY requests went to that origin. If zero requests, it's definitively unused—recommend removal. If requests exist but loaded late, the preconnect may still be valuable.

For detailed request info:

get_network_request(reqid: <id>)

Phase 4: Accessibility Snapshot

Take an accessibility tree snapshot:

take_snapshot(verbose: true)

Flag high-level gaps:

Missing or duplicate ARIA IDs
Elements with poor contrast ratios (check against WCAG AA: 4.5:1 for normal text, 3:1 for large text)
Focus traps or missing focus indicators
Interactive elements without accessible names

Phase 5: Codebase Analysis

Skip if auditing a third-party site without codebase access.

Analyze the codebase to understand where improvements can be made.

Detect Framework & Bundler

Search for configuration files to identify the stack:

Tool	Config Files
Webpack	`webpack.config.js`, `webpack.*.js`
Vite	`vite.config.js`, `vite.config.ts`
Rollup	`rollup.config.js`, `rollup.config.mjs`
esbuild	`esbuild.config.js`, build scripts with `esbuild`
Parcel	`.parcelrc`, `package.json` (parcel field)
Next.js	`next.config.js`, `next.config.mjs`
Nuxt	`nuxt.config.js`, `nuxt.config.ts`
SvelteKit	`svelte.config.js`
Astro	`astro.config.mjs`

Also check package.json for framework dependencies and build scripts.

Tree-Shaking & Dead Code

Webpack: Check for mode: 'production', sideEffects in package.json, usedExports optimization
Vite/Rollup: Tree-shaking enabled by default; check for treeshake options
Look for: Barrel files (index.js re-exports), large utility libraries imported wholesale (lodash, moment)

Unused JS/CSS

Check for CSS-in-JS vs. static CSS extraction
Look for PurgeCSS/UnCSS configuration (Tailwind's content config)
Identify dynamic imports vs. eager loading

Polyfills

Check for @babel/preset-env targets and useBuiltIns setting
Look for core-js imports (often oversized)
Check browserslist config for overly broad targeting

Compression & Minification

Check for terser, esbuild, or swc minification
Look for gzip/brotli compression in build output or server config
Check for source maps in production builds (should be external or disabled)

Output Format

Present findings as:

Core Web Vitals Summary - Table with metric, value, and rating (good/needs-improvement/poor)
Top Issues - Prioritized list of problems with estimated impact (high/medium/low)
Recommendations - Specific, actionable fixes with code snippets or config changes
Codebase Findings - Framework/bundler detected, optimization opportunities (omit if no codebase access)

Installs

Installs 5.6K

Global Rank #363 of 600

Security Audit

ath Safe

socket Safe

Alerts: 0 Score: 90

snyk Medium

zeroleaks Safe

Score: 93

View Source

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How to use this skill

Install web-perf by running npx skills add cloudflare/skills --skill web-perf in your project directory. Run the install command above in your project directory. The skill file will be downloaded from GitHub and placed in your project.

No configuration needed. Your AI agent (Claude Code, Cursor, Windsurf, etc.) automatically detects installed skills and uses them as context when generating code.

The skill enhances your agent's understanding of web-perf, helping it follow established patterns, avoid common mistakes, and produce production-ready output.

What you get

Skills are plain-text instruction files — not executable code. They encode expert knowledge about frameworks, languages, or tools that your AI agent reads to improve its output. This means zero runtime overhead, no dependency conflicts, and full transparency: you can read and review every instruction before installing.

Compatibility

This skill works with any AI coding agent that supports the skills.sh format, including Claude Code (Anthropic), Cursor, Windsurf, Cline, Aider, and other tools that read project-level context files. Skills are framework-agnostic at the transport level — the content inside determines which language or framework it applies to.

Data sourced from the skills.sh registry and GitHub. Install counts and security audits are updated regularly.

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web-perf AI Agent Skill

Web Performance Audit

Retrieval Sources

FIRST: Verify MCP Tools Available

Key Guidelines

Quick Reference

Workflow

Phase 1: Performance Trace

Phase 2: Core Web Vitals Analysis

Phase 3: Network Analysis

Phase 4: Accessibility Snapshot

Phase 5: Codebase Analysis

Detect Framework & Bundler

Tree-Shaking & Dead Code

Unused JS/CSS

Polyfills

Compression & Minification

Output Format

Installs

Security Audit

View Source

Power your AI Agents with the best open-source models.

How to use this skill

What you get

Compatibility

Chat with 100+ AI Models in one App.

Power your AI Agents with
the best open-source models.