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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds beyond that: it fixes the cardinality ('exactly one book'), clarifies the lookup key is lang+slug, and states the return shape ('one catalog record object'), which helps the agent plan a fetch decision. No mention of auth or rate limits, 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 identity, then labeled When-to-use / Do-not-use / Returns segments. Every clause carries routing or expectation-setting information; 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?

With no output schema, the description compensates by enumerating the returned fields and stating the return shape, so the agent knows what it will get. Combined with the routing guidance, nothing needed to invoke this correctly is missing.

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% and both parameters (lang, slug) are documented there, so the schema does the heavy lifting. The description only implies the lang+slug requirement in prose without adding format or validation detail beyond what the schema already says. Baseline 3 is correct.

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 precise verb+resource: returns metadata for exactly one book, and enumerates the fields (title, author, genre, chapter_count, word_count, source URL, access URLs). It also names the sibling tools it is not (cyberlibrary_get_chapter, cyberlibrary_get_markdown), so an agent can route without opening any 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?

Explicit 'When to use' conditions (you have lang+slug and need to judge whether a book is worth fetching, or need chapter_count before pulling a chapter) and an explicit 'Do not use' clause pointing at the two content-retrieval siblings. Both the trigger and the exclusions are stated, not inferred.

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