Analyze a Page with Lighthouse

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

Annotations already mark the tool read-only, idempotent, and non-destructive. The description adds that the Google API is contacted and results may come from a local cache, setting expectations about external dependency and possible staleness. No contradiction with the annotations.

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?

Four short sentences: purpose, report-mode guidance, a concrete example, and an external-behavior caveat. Each sentence earns its place, and the core purpose is front-loaded.

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?

With a fully described schema, enums, annotations covering safety, and an output schema present, the only operational context an agent needs is report-mode selection and the external API/cache behavior — both provided. Nothing significant is missing for correct selection and invocation.

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 the baseline is 3. The description adds meaning by mapping report enum values to intended use cases and giving a concrete example ('analyze a mobile product page and return the three most useful remediation steps'), which clarifies strategy and report selection beyond the schema.

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?

The description opens with 'Run a PageSpeed Insights Lighthouse analysis for one public page' — a specific verb, resource, and scope. Saying 'one public page' differentiates it from batch and compare siblings, and the list of report modes clarifies its capabilities further.

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?

The description gives explicit decision rules for the report parameter ('summary for a health check', 'recommendations for a prioritized fix list'), which tells an agent which mode fits a goal. It does not mention sibling tools by name, but 'one public page' implies single-page scope versus batch analysis.

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