run_lighthouse

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

With no annotations provided, the description carries the full burden and does well by disclosing key behavioral traits: it lists the comprehensive return data (scores, metrics, opportunities, diagnostics), mentions the prerequisite (Lighthouse CLI installation), and describes the mobile/desktop execution approach. However, it doesn't cover rate limits, error conditions, or execution time expectations.

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?

The description is perfectly structured and concise: it starts with the core purpose, then details the returns in a bulleted format, provides usage guidance, and ends with a prerequisite note. Every sentence earns its place with no wasted words.

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?

Given the tool's complexity (performance audit with multiple metrics) and no output schema, the description does an excellent job explaining what will be returned. However, without annotations covering safety/behavioral aspects and no output schema, it could benefit from more detail about error handling or execution characteristics.

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 description coverage is 100%, so the schema already documents all 4 parameters thoroughly. The description doesn't add any parameter-specific information beyond what's in the schema, maintaining the baseline score of 3 for high schema coverage situations.

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 clearly states the specific action ('Run a Lighthouse performance audit') on a specific resource ('on a URL'), distinguishing it from sibling tools like analyze_page or crawl_site by focusing on comprehensive performance analysis with specific metrics and categories.

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 provides clear context for when to use this tool ('for performance analysis') and advises running separately for mobile/desktop if both matter, but doesn't explicitly state when not to use it or name specific alternatives among the sibling tools.

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