Core Web Vitals analysis powered by Lighthouse.
LightScout MCP
Part of the TestScout MCP Suite — AI-powered QA tools for modern development teams.
Core Web Vitals analysis powered by Lighthouse. Runs as an MCP server for AI coding tools (Claude Code, Cursor, Windsurf, etc.) or as a standalone CLI for CI pipelines and terminals. Four tools: analyze a URL, compare two URLs, check against thresholds, or crawl an entire site.
Requirements
- Node.js >= 18
- Google Chrome or Chromium
MCP Server Setup
Claude Code
claude mcp add lightscout -- npx -y lightscout-mcp
Cursor, VS Code, Windsurf, Cline, Roo Code, Gemini CLI
All use the same mcpServers JSON format. Add this to the appropriate config file:
{
"mcpServers": {
"lightscout": {
"command": "npx",
"args": ["-y", "lightscout-mcp"]
}
}
}
| Client | Config file |
|---|---|
| Cursor | ~/.cursor/mcp.json |
| VS Code (Copilot) | .vscode/mcp.json |
| Windsurf | ~/.codeium/windsurf/mcp_config.json |
| Cline | Settings > MCP > Edit Config |
| Roo Code | .roo/mcp.json |
| Gemini CLI | ~/.gemini/settings.json |
Zed
Zed uses context_servers instead of mcpServers:
{
"context_servers": {
"lightscout": {
"command": "npx",
"args": ["-y", "lightscout-mcp"]
}
}
}
CLI
Install
npm install -g lightscout-mcp
Try without installing
npx -p lightscout-mcp lightscout analyze https://example.com
Commands
lightscout analyze <url> [--device mobile|desktop] [--categories perf,a11y,seo,best-practices]
lightscout compare <urlA> [urlB] [--device mobile|desktop]
lightscout crawl <url> [--max-pages N] [--device mobile|desktop]
lightscout check <url> [--perf 90] [--lcp 2500] [--fcp 3000] [--cls 0.1] [--tbt 300] [--ttfb 1800]
Examples
Analyze a single page:
lightscout analyze https://example.com
lightscout analyze https://example.com --device desktop --categories performance,accessibility
Compare two URLs, or the same URL on mobile vs desktop:
lightscout compare https://a.com https://b.com
lightscout compare https://example.com # mobile vs desktop
Crawl a site and audit discovered pages:
lightscout crawl https://example.com --max-pages 5
CI quality gate (exits 1 on failure):
lightscout check https://example.com --perf 90 --lcp 2500
Tools
analyze_performance
Run Lighthouse on a URL. Returns performance scores, Core Web Vitals (LCP, FCP, CLS, TBT, SI, TTFB) with good/needs-improvement/poor ratings, top recommendations sorted by impact, and diagnostics.
| Parameter | Type | Required | Description |
|---|---|---|---|
url |
string | yes | URL to analyze |
device |
"mobile" | "desktop" |
no | Device emulation (default: mobile) |
categories |
string[] | no | Lighthouse categories (default: ["performance"]) |
compare_performance
Compare Core Web Vitals between two URLs, or the same URL on mobile vs desktop. Shows per-metric deltas with winner indicators.
| Parameter | Type | Required | Description |
|---|---|---|---|
urlA |
string | yes | First URL |
urlB |
string | no | Second URL. If omitted, compares urlA mobile vs desktop |
device |
"mobile" | "desktop" |
no | Device emulation when comparing two URLs (default: mobile) |
check_threshold
Pass/fail check against performance thresholds. Useful for CI quality gates.
| Parameter | Type
Tools (3)
analyze_performanceRun Lighthouse on a URL to get performance scores and Core Web Vitals.compare_performanceCompare Core Web Vitals between two URLs or device types.check_thresholdPass/fail check against performance thresholds for CI quality gates.Configuration
{"mcpServers": {"lightscout": {"command": "npx", "args": ["-y", "lightscout-mcp"]}}}