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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), so the bar is lower. The description still adds useful behavior: the output is a comparison grid, the input is capped at two or three books, and it declares the default aspects. It does not discuss pagination, rate limits, or failure behavior for unknown slugs, keeping it short of a 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 action, then aspects, then usage routing, then compact examples — each block has a distinct job. No sentence is redundant, and the aspect glossary replaces what would otherwise be vague enumeration.

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?

An output schema exists so return values need no explanation, and the description closes the remaining gaps: the 2–3 book limit, defaults, aspect meanings, and sibling routing. For a two-parameter read-only compare tool this is fully sufficient to invoke 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 already 100%, yet the description goes well beyond it by defining what each aspect actually yields: 'difficulty' includes overall and per-dimension scores plus hardest/easiest dimensions, 'themes' splits shared vs distinct, 'length' gives word count and reading time, 'style' covers genre and literary regard. Two concrete call examples show the id-array shape and default-vs-explicit aspects.

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 ('Sets two or three books side by side and shows them as a comparison grid') and enumerates exactly what is compared via the five named aspects. It is immediately distinguishable from sibling read tools like get_book_details and search_books.

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 states when to use it ('compare specific books, which of them is harder or longer, or which to read first') and routes to the correct alternatives for adjacent intents: get_book_details for a single book, search_books to find books. Nothing 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.