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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds useful platform-specific behavior: Android uses cat_key, while iOS uses genre_id plus optional device_type.

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?

It is front-loaded with the core action, followed by necessary platform-specific details and a compact example. Every sentence contributes to correct invocation without unnecessary verbosity.

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?

For a 9-parameter tool with 100% schema coverage and rich annotations, the description covers the main invocation ambiguity: Android vs iOS category parameters. It does not describe return values or pagination behavior, but the schema documents page and limit, and no output schema exists.

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 baseline would be 3. The description goes beyond the schema by giving a concrete invocation example and clarifying platform-specific parameter usage such as cat_key for Android and genre_id for iOS.

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: 'Get a ranked top-chart list' for a country and category. It also names the chart types and platform distinction, making it clearly distinguishable from sibling app lookup/search tools.

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?

Usage is implied by the purpose: retrieve ranked store charts for a country/category. However, it does not explicitly say when to choose this tool over alternatives such as fortytwo_app_search or fortytwo_app_lookup, nor does it state any exclusions.

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