compare_books

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

Beyond the readOnly/idempotent annotations, the description discloses the ranking logic (best-to-worst by average rating), the computed percentages (pct_positive, pct_critical), and the refusal behavior for >10 ids. These are operational details an agent could not infer from the annotations or schema. No contradiction exists.

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 three sentences, each with a distinct job: purpose, return semantics, and call limits. The most important information is front-loaded. No sentence is 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?

For a one-parameter read-only tool with an output schema already available, the description covers invocation limits, return semantics, and the source of ids. Nothing needed for a correct call is missing. The output schema removes the need to enumerate returned fields in prose.

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 only provides a type and title for book_ids with 0% description coverage, so the description carries the explanatory burden. It supplies the valid count range (2-10), the refusal behavior, and the provenance ('from search_books etc.'). It does not define the exact id format, but for a single string-array param this is sufficient.

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 opening sentence uses a specific verb ('Compare') and resource ('books') and immediately narrows the scope to rating and rating distribution. The second sentence specifies a ranked best-to-worst output, which differentiates it from sibling tools like get_book or similar_books. It even points at sibling search_books for id provenance, so an agent can select it confidently.

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 clearly states the intended call pattern: pass 2-10 book ids, and gives a hard behavioral rule for exceeding that range ('more than 10 is refused rather than silently trimmed, so split the call'). It does not explicitly enumerate when-not-to-use alternatives, so it falls just short of a full 5. Still, the context for when this tool is appropriate is unambiguous.

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