web-perf
Measures Core Web Vitals and identifies render-blocking resources, network chains, layout shifts, and caching issues.
- Analyzes performance traces using Chrome DevTools MCP to extract FCP, LCP, TBT, CLS, Speed Index, and TTFB with detailed breakdowns
- Identifies render-blocking CSS/JS, network dependency chains, missing preloads, and caching header gaps through network request inspection
- Detects layout shift culprits (images without dimensions, injected content, font swaps) and accessibility gaps via DOM snapshots
- Requires chrome-devtools MCP server configured; provides checklist-driven audit workflow across performance, network, and accessibility phases
- Prioritizes findings by estimated impact and skips non-issues; biases toward live documentation over pre-trained thresholds
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Your knowledge of web performance metrics, thresholds, and tooling APIs may be outdated.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
Discover available browser and performance tools before starting. Use the capabilities available for the requested audit. If trace tools are unavailable, continue any useful source or network analysis and state which measurements could not be collected.
If the user wants Chrome DevTools MCP setup, consult its installation guide and use the latest package version. Only change MCP configuration when setup is within the user's authorized scope; otherwise ask first. For clients using command and args, an example server entry is: