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

Annotations already declare readOnly, idempotent, and non-destructive, and the description adds significant behavioral context: the data source (Apple's RSS Marketing Tools feed), the maximum of 100 entries, and the exact return fields (title, author, Apple id, genres, release date, artwork URL, and link). This exceeds the baseline and provides a complete behavioral picture.

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?

Two dense sentences with no redundancy. The first sentence captures source, scope, and limits; the second lists return fields and the core purpose. Information is front-loaded and every phrase earns its place.

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 a simple tool with all optional parameters and an output schema present, the description covers everything needed: source, scope, defaults, limits, and return contents. It leaves no significant gaps for an agent to wonder about selection or invocation.

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 only 33%, but the description compensates fully: it clarifies limit (up to 100), country ('one storefront country'), and free_or_paid (top-free default or top-paid). This gives every parameter meaningful semantics beyond the schema's minimal descriptions.

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 clearly identifies the tool as an Apple Books chart reader from Apple's RSS feed, specifying top-free or top-paid ebooks and up to 100 entries. It distinguishes itself from sibling tools like top_movies and top_podcasts by focusing on ebooks and explicitly stating it 'answers which ebooks are topping the charts today.'

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 provides clear context: it is for Apple Books charts in a single storefront country, with a default chart type and entry limit. It does not explicitly mention alternatives or when not to use it, but the scope makes appropriate usage obvious, so it earns a 4 rather than a 3.

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