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

Annotations already declare readOnly/idempotent/destructive-false, so the safety profile is covered. The description adds real behavioral context beyond that: the pagination model, a concrete scale example (en = 25 pages x 2500 books), and the return shape with books trimmed to `limit`. It stops short of stating ordering of results or what happens when `page` exceeds total_pages, so not a full 5.

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 core purpose, then when-to-use, then exclusions, then return shape. Each sentence carries distinct information and there is no 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?

There is no output schema, so the description carries the return-shape burden and does so explicitly with field names. Combined with annotations covering safety and the schema covering all three params, an agent has everything needed to call it correctly.

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 meaning beyond the schema: the scale example ties `page` and the default 100 `limit` to real pagination behavior, and 'books trimmed to `limit`' clarifies the interaction between limit and the returned count. It still doesn't document zero-based vs 1-based beyond the schema or overflow behavior for `limit`.

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 ('One page of the book catalog for a language') and immediately clarifies the pagination model (large languages paginated, small ones a single shard). It is readily distinguishable from siblings by naming cyberlibrary_fulltext_search and cyberlibrary_book_meta as the not-this alternatives.

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?

Explicitly gives both a 'When to use' (browse/sample a language, locate a title) and a 'Do not use' with two named alternatives and their selecting conditions. Nothing about routing is left to inference.

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