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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context by describing the returned data, including daily rank movement, snapshot date, and the specific fields (e.g., delta vs. yesterday, is_new), which matters because no output schema is provided.

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 core purpose in the first sentence, followed by useful return-field and parameter details. The long parenthetical list of returned fields is slightly dense, but it earns its place because there is no output schema to document the response.

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?

Given the lack of an output schema, the description helpfully enumerates the returned fields and explains the category and collection semantics. It does not mention the limit parameter or how to discover valid category values (e.g., via list_top_chart_categories), but those gaps are minor because the schema covers parameter details and the core return behavior is described.

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 all five parameters. The description largely repeats the schema's parameter descriptions, including the same examples (iTunes genre id '6014', Google Play category 'GAME') and defaults (OVERALL, free), adding no meaningful semantic detail beyond what the structured schema provides.

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: retrieving a store top-chart ranking for a given country, category, and collection. It names the two stores (App Store or Google Play) and the chart types, which distinguishes it from sibling tools like list_top_chart_categories and the keyword-rank-history 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?

The description implies the tool's use case (fetching a top-chart ranking) and provides parameter defaults, but it does not explicitly state when to choose this tool over alternatives or when not to use it. No sibling tool is named as an alternative, so the guidance remains implicit.

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