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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so the safety profile is covered. Beyond that the description adds nothing behavioral — no indication of the time window covered, whether the value is cached or live, or what dimensions the KPI is broken down by.

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?

Extremely short and front-loaded, with no filler preamble. The only mild redundancy is the verbatim Korean restatement of the same phrase, which duplicates rather than extends the meaning.

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 and no parameters, so the description is the only source of information about what an agent gets back. It does not say whether the result is a single number, a time series, or a breakdown, leaving the return shape unknown for a metric-fetching tool.

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 tool takes zero parameters, so there is no parameter semantics burden and the baseline is 4. The description neither needs to nor does explain any inputs.

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 names a specific concept (North Star growth KPI), so an agent knows this returns a growth metric rather than raw member data. However, it is a bare noun phrase with no verb (fetch/get/read) and gives no basis for distinguishing it from siblings like members_summary or members_cross_platform.

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?

There is no when-to-use guidance, no statement of what question this answers, and no naming of alternatives such as members_summary. Usage must be entirely inferred from the name.

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