ANR rate

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

Annotations already establish readOnly, idempotent, non-destructive behavior, so the bar is lower. The description adds meaningful context beyond them: the data is daily, aggregates are user-weighted, and rates are expressed as fractions (0.01 = 1%), which prevents a serious misreading of the output. It does not cover latency, data freshness, or rate limits.

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?

Two tightly written sentences; the source and returned shape come first, with the unit clarification front-loaded enough that no line is wasted.

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 read-only metric tool with full schema coverage and annotations covering safety, the description supplies purpose, units, and aggregation windows. With no output schema, a brief note on the returned structure or how dimensions affect the result would close the remaining gap, but the essentials are present.

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 days, filter, dimensions, and package_name are already documented. The description adds no syntax or semantic detail about these parameters, so the baseline 3 applies.

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?

States a specific metric (ANR rate), its source (Android vitals / Play Developer Reporting API), and the exact returned shape (daily plus 7- and 28-day user-weighted values). This clearly differentiates it from siblings like crash_rate, slow_start_rate, and slow_rendering_rate without opening any schema.

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 definition implies this is the tool for ANR metrics, but gives no explicit when-to-use guidance, no mention of the sibling vitals tools, and no statement about prerequisites such as package setup. Usage is inferable only from the distinctive metric name.

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