browser_perf_get_performance_metrics

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

No annotations are provided, so the description bears the full burden. It states the tool gets metrics and lists them, but does not disclose whether it is read-only, requires a loaded page, or has side effects. Basic coverage, but more could be said.

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 a single sentence that is direct and informative. Including a reference to browser_docs adds a small overhead but provides helpful direction. Slightly over the minimal length, but still concise.

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 no output schema and no annotations, the description should explain the return format and behavior. It lists metrics but does not describe the structure of the output (e.g., object with fields, units). The reference to browser_docs is insufficient for immediate completeness.

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?

There are no parameters (100% schema coverage), so the baseline score is 4. The description adds value by specifying which metrics are retrieved, compensating for the lack of parameters.

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 uses a specific verb 'Get' and resource 'web vitals and navigation timing', listing specific metrics (FCP, LCP, CLS, TTFB). This clearly distinguishes it from sibling tools like browser_perf_get_heap_usage, which focus on other aspects.

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?

No explicit guidance on when to use this tool versus alternatives like browser_perf_get_metrics. The description implies usage for web vitals, but lacks exclusionary or comparative context. The reference to browser_docs suggests further help is external.

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