web-perf

# Web Performance Audit Your knowledge of web performance metrics, thresholds, and tooling APIs may be outdated.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: ```json "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" n...