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

Annotations already establish that the tool is read-only, idempotent, and non-destructive. The description adds value by disclosing the concrete return fields, including the notable 'whether its full text is indexed here' behavior, which is not inferable from the input schema. It does not cover not-found or error behavior, but the annotation coverage lowers that burden.

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 a single front-loaded sentence with the field list in a parenthetical. There is no filler, no repetition of schema details, and every phrase contributes to understanding what the tool returns.

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?

For a simple single-parameter lookup with strong annotations, the description is complete: it identifies the required input and the full set of returned metadata fields. Since there is no output schema, the description appropriately carries the return-value information needed by the agent.

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?

The input schema already documents gutenberg_id with 100% coverage and a concrete example ('84 (Frankenstein)'). The description only restates that the parameter is a Project Gutenberg id and adds no additional syntax or format details, so the baseline score of 3 is appropriate.

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 states a specific verb and resource: 'Get full catalog metadata for a single book by its Project Gutenberg id.' It enumerates the exact metadata fields, making it clearly distinguishable from sibling tools like book_search, book_get_text, and book_fulltext_search.

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 makes the usage context clear: use this when you already have a Gutenberg id and need catalog metadata for one book. It does not explicitly name alternatives or exclusions, but the 'single book by id' framing is sufficient to differentiate it from search and text-retrieval siblings.

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