lighthouse

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Adds rich context beyond annotations: launch-mode requirement, new-tab loading, first-call npx download, 20-60s duration, file output paths. Annotations say destructiveHint=true (odd for a read-only audit), but the description doesn't contradict this; it explains the operational profile clearly. Could note why destructive is true (file writes?) but the file output mentions that.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Dense but front-loaded: purpose first, then use constraints, then timing. Three sentences cover a lot of ground efficiently. Slightly overpacked but every sentence earns its place for a complex tool.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Complete for a complex audit tool: covers what it returns (scores, lab metrics, failing audits), file outputs, prerequisites (launch mode, DevTools port), timing, and first-call overhead. No output schema, but the description explains return content. Missing only explicit alternative comparison beyond chrome-devtools-mcp.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline 3. The description adds value by explaining the 'url' default (target tab's URL), 'categories' default (all four), 'form_factor' default (mobile emulation of mid-range phone on slow 4G like PageSpeed), and 'save_to' behavior (.report.json/.report.html). More than the schema alone in some cases.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (Run) and resource (full Lighthouse audit) with the exact scope (performance, accessibility, best practices, SEO) and output form (scores, five lab metrics, failing audits). Explicitly contrasts itself with chrome-devtools-mcp, differentiating from siblings like 'audit' and 'perf_trace'.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides strong context: works only in launch mode (chrome-bridge --launch), loads in a new tab, takes 20-60s, first call downloads via npx. These are critical usage constraints. Doesn't explicitly name alternatives like 'perf_trace' or 'audit' but the chrome-devtools-mcp contrast implies positioning.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.