get_app_perf_metrics

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions that the tool returns 'Xcode-style metrics data with values per device and percentile' but does not state whether the operation is read-only, requires authentication, or has any side effects. The safety and authorization profile is not disclosed.

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 two sentences long, front-loaded with the primary action and examples, and contains no redundant information. Every sentence serves a purpose.

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?

There is no output schema, so the description should explain return format details. While it mentions 'Xcode-style metrics data with values per device and percentile', it does not elaborate on pagination, interpretation of metrics, or possible error conditions. For a tool with 4 parameters, this is adequate but not thorough.

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 each parameter. The description adds value by explaining the overall scope ('app-level aggregate metrics across all builds'), which contextualizes the appId and metricType parameters. However, it does not elaborate on enum values or additional constraints beyond what the schema provides.

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 retrieves performance and power metrics for an app, listing specific metric types (launch time, memory, battery, hangs). It distinguishes from the sibling tool get_build_perf_metrics by emphasizing 'app-level aggregate metrics across all builds'.

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 recommends using this tool for 'app-level aggregate metrics across all builds', implying it is not for build-specific analysis. While it does not name the sibling tool get_build_perf_metrics directly, the context and sibling list provide clear differentiation.

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