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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), so the description's added value is its disclosure of the return payload — developer contact info, ratings, installs, price, version, size, dates, description — with a genuine platform split (iOS adds star histogram, languages, required iOS version). It adds real context beyond the annotations, though it says nothing about error behaviour or rate limiting for an open-world fetch.

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-loaded with the one-line purpose, then two parallel platform-specific sentences. The long comma-separated field lists are dense but each item is informative; the enumeration is doing real work in the absence of an output schema.

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?

No output schema exists, and the description compensates well by enumerating what comes back for each store and how to identify the app. What's missing is failure behaviour (invalid/unknown id) and any note on freshness or caching — minor for a read-only single-record lookup.

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?

With one parameter at 100% schema description coverage, the schema already carries the Android-vs-iOS meaning and both examples. The description largely restates that mapping; it adds the nuance that the returned fields differ by platform, but no new input syntax or constraints.

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 and resource ('Get details of one app') and immediately distinguishes the two input flavours (Android package name vs. numeric App Store id). It doesn't explicitly contrast itself with close siblings like get_app_privacy, get_app_reviews, or get_developer_apps, so an agent must infer that boundary from the names alone.

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 tells you what identifier to supply per platform, which is practical invocation guidance, but it never says when to reach for this tool versus the sibling review/privacy/developer tools, nor what to do if the app isn't found. Usage is implied rather than stated.

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