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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), yet the description adds substantial behavior: English-language filtering, one-per-author and one-per-series dedup, ordering by picked_from (shelf before subjects), popular-over-obscure preference, and explicit genre exclusions for novels. This is exactly the kind of context annotations cannot convey.

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-loaded with the purpose and usage examples, and every clause carries information (dedup rules, ordering, exclusions). It is a dense block that borders on a wall of text, which slightly hurts scanability, but nothing is filler.

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 still explains the shape of results via the picked_from/because conventions, and it covers all five optional parameters. An agent has everything needed to call it and interpret the response.

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 baseline is 3, but the description adds real meaning: it clarifies that title accepts common informal titles ('1984', 'The Sorcerer's Stone') and that same_author controls whether other books by the author are excluded by default. That goes beyond the plain field definitions.

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 ('find similar books') and pins the scope to 'books like one the user enjoyed, or for a genre'. An agent can distinguish it from bookslikethis_get_book and get_author_books without opening a 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?

Gives concrete trigger examples ('books like The Martian', 'a good cosy mystery') and tells the caller to 'give title or subject', which is clear usage context. It does not, however, explicitly compare against the sibling tools get_book/get_author_books, so there is no when-not guidance.

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