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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive behavior, so the safety profile is covered. The description adds useful context by listing the returned fields and specifying the identifier formats needed per platform. It does not describe missing-app behavior or rate limits, but those are secondary here.

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?

The description is front-loaded with the purpose, then gives platform-specific ID guidance, then an example. It is appropriately sized and nearly every sentence earns its place, though the example partially duplicates the schema's own examples.

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 no output schema, the description usefully enumerates the returned fields. Combined with rich annotations and 100% parameter schema coverage, an agent has enough information to invoke the tool correctly without needing additional behavioral details.

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 the schema already documents app_id, _apiKey, platform, and app_country. The description reinforces the platform-specific app_id format and includes an example call, but it adds little beyond what the structured schema already provides. Baseline 3 is appropriate.

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 states a specific verb and resource: lookup full details for a single mobile app. It also enumerates returned fields and scopes the tool to one app, which distinguishes it from sibling search/chart tools. An agent can tell what this tool does without opening the 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?

The description gives clear context for when to use it: when you need full details for a single app and have either an Android package name or iOS numeric App Store ID. It does not explicitly name alternatives such as fortytwo_app_search or say when not to use this tool, so it stops short of full routing guidance.

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