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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is known. The description adds useful behavioral context: it clarifies output type ('NOT passages'), mentions search fields ('titles, authors, subjects, and (as a secondary signal) translated text'), and describes pagination metadata ('total_matches... + returned... + offset'). It does not contradict annotations.

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?

The description is front-loaded with the key message and uses visual separators (—, →) to structure alternatives. It covers purpose, alternatives, query tips, and pagination in about 100 words without fluff. Slightly dense but every sentence 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?

With 8 parameters and no output schema, the description carries the burden of explaining return behavior. It does explain the pagination envelope and search scope, and provides explicit routing to siblings. It could mention the book object's fields (e.g., title, author) more explicitly, but given the tool's straightforward 'list of books' nature, this is adequate.

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 high (88%), so the baseline is 3. The description adds value by giving query formulation tips ('single distinctive words or short phrases work best... quoted phrases match exactly'), which go beyond the schema's query description. It also explains how offset and total_matches relate to pagination, adding semantics to the pagination parameters.

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 opens with 'RETURNS A LIST OF BOOKS (works on a topic) — NOT passages,' clearly stating the tool's verb and resource. It distinguishes itself by explicitly contrasting with search_translations and search_concept, and by stating 'PICK THIS to discover which works exist on a subject.' This is specific and differentiates from siblings.

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 explicit when-to-use guidance: 'PICK THIS to discover which works exist on a subject.' It also names alternatives: 'use search_translations (exact words) or search_concept (by meaning); if the user already named an author/work, call get_book directly (or list_books to find the ID).' This is a model of usage guidance.

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