profile_page_performance

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

With no annotations provided, the description carries the full burden and excels by disclosing multiple behavioral traits: side effects ('may temporarily disable cache; impacts page memory/CPU'), prerequisites ('requires an active Chrome tab; trace recording uses background bandwidth'), and return format ('JSON with vitals, blocking time, and top 5 long tasks'). This provides comprehensive behavioral context beyond basic functionality.

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 well-structured and appropriately sized, with key information front-loaded (purpose, side effects, prerequisites) followed by usage guidance. Every sentence adds value, though it could be slightly more concise by combining some clauses about prerequisites and side effects.

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?

For a tool with no annotations and no output schema, the description provides excellent context about behavior, side effects, prerequisites, and return format. It covers what the tool does, when to use it, what to expect, and what alternatives exist. The only minor gap is not explicitly mentioning that all parameters are optional (though this is clear from the schema).

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?

The schema description coverage is 100%, providing detailed documentation for all three parameters. The description doesn't add any parameter-specific information beyond what's already in the schema, so it meets the baseline expectation without adding extra value. No parameters are mentioned in the description text itself.

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 tool's purpose with specific verbs ('Records a performance trace', 'calculating Core Web Vitals', 'identifying Long Tasks') and distinguishes it from siblings by focusing on performance profiling rather than DOM manipulation, network monitoring, or other browser operations listed among sibling tools.

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 explicitly states when to use this tool ('Use this to optimize performance, identify bottlenecks, measure cold starts') and provides clear alternatives ('browser DevTools Performance tab, real user monitoring (RUM)'), giving the agent specific guidance on appropriate contexts and available options.

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