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

Annotations declare readOnlyHint=true and openWorldHint=true, so safety and world-access are already covered. The description adds value by enumerating the returned data categories, but says nothing about rate limits, caching, or how missing/region-restricted apps behave. Adequate but not rich beyond 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, then the return contents, then the sibling routing and defaults. Slightly redundant by restating AppID and Country definitions already in the schema, but overall well-organized and no major waste.

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?

With an output schema present, the description needn't explain return values in detail, yet it usefully enumerates them, and the sibling routing covers the main ambiguity (ratings vs reviews). Complete enough for a read-only single-app 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?

Schema coverage is 100%, so all three parameters are already documented in the schema, and the description largely repeats them (AppID example, Country ISO-2, default us). No additional syntax or edge-case detail beyond the schema. Baseline 3 when schema does the heavy lifting.

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 ('Returns normalized app metadata from a Google Play details page') and enumerates the returned content types (installs, ratings, pricing, version, media, comments, recommendation rails), clearly distinguishing it from siblings like googleplay_ratings.

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?

Explicitly routes the agent: points to /googleplay/ratings for per-device ratings-and-reviews, and to googleplay_search for searching. States defaults (country=us, lang=en). Nothing left to inference.

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