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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed world), so the extra value here is the retention window: 3 days on free, 30 with Pro. That is genuinely invocation-relevant, since the tool exposes no date parameters and the lookback is fixed by plan. It still says nothing about rate limits or whether gaps in days are returned.

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 short sentences with no filler, and the payload content is front-loaded ahead of the plan caveat. Slightly terse for what it omits, but nothing 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?

There is no output schema, so the description is the only source on return values. It names the three metrics well but does not say the response is a per-day time series, what ordering it uses, or how missing days appear (nulls vs omitted), which leaves the shape partially inferred.

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 0%, so the description must carry the burden of explaining the two parameters. It only implicitly maps them via 'one app in one storefront'; it never states that appId must be a numeric app ID or that country is a two-letter code, nor which storefronts are supported.

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 the exact resource and metrics returned: daily average rating, rating count and review count, scoped to one app and one storefront. This distinguishes it from data siblings like get_app_estimates or get_app_ranks. It lacks an explicit verb but the purpose is unambiguous.

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 statement of when to call this versus alternatives, and no prerequisites (e.g. whether the app must be tracked). The only conditional sentence is about plan-based data depth, which is a data-availability note, not usage guidance.

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