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

Annotations already declare readOnly/idempotent/openWorld, so the safety profile is covered. The description adds genuinely useful context beyond that: it is a live external call against Gutendex, results are ranked by keyword relevance then download popularity, and it discloses the returned fields. It stops short of mentioning rate limits or pagination behavior.

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?

Three sentences, each earning its place: scope, ranking/return behavior, and the sibling routing. Front-loaded with the core action and the discriminating alternative placed last, which is the right order.

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?

No output schema exists, yet the description enumerates the returned fields (Gutenberg id, title, author(s), language, download count), and covers source, ranking, and sibling disambiguation. Nothing an agent needs to call 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%, so all five parameters (including limit's default/max) are already documented in the schema. The description's mention of title/author/subject keyword and the optional author/subject/language filters largely restates that. Baseline 3 is appropriate when the schema carries the semantics.

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 ('Search the full Project Gutenberg catalog ... by title / author / subject keyword') with scope (~78,500 books) and source (Gutendex). It explicitly distinguishes itself from the sibling book_fulltext_search, so an agent can route correctly without opening either 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?

Names the alternative (book_fulltext_search) and the condition that selects it ('to search inside the locally indexed top books'). This is an explicit when/when-not split, so the agent knows which of the two book tools to pick.

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