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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered by structured fields. The description adds the returned content shape, but says nothing about rate limits, auth, or storefront edge cases, so it adds only modest value beyond the annotations.

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?

Front-loads the purpose sentence, then parameter semantics, then the sibling routing hint — a sensible order with no wasted filler. It repeats schema content verbatim, which is mildly redundant but not harmful.

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?

An output schema exists so return-value explanation is not required, and annotations carry the safety profile; the description covers purpose, identifier guidance, and the key sibling alternative. Only minor gaps (no rate-limit or auth note) remain.

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 all four parameters (ID, Lang, AppID, Country) are already documented with examples in the schema. The description restates ID/Country details but adds no format or constraint meaning beyond what the schema provides; 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 verb (returns) and an exact resource — the total ratings count and the 1-5 star histogram shown on the App Store product page. It explicitly distinguishes itself from the sibling appstore_reviews, so an agent can separate the two without opening either 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?

Names the alternative appstore_reviews and the boundary (reviews vs. rating histogram), and instructs 'Provide id or app_id', which tells the agent how to satisfy the identifier. It stops short of stating when-not to use it, but the routing context is clear.

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