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

Annotations already declare openWorldHint=true and destructiveHint=false; the description adds operational scope not in the schema, notably the API-key library list and the default behavior when systemids is omitted ('searches all libraries'). readOnlyHint=false is the schema default and does not assert mutation, so it is consistent with a search operation. It does not, however, describe result format, pagination interaction between limit/offset, or rate limits.

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?

Purpose is front-loaded in the first sentence, and the remaining lines are short and purposeful (scope note plus library list). The bulleted list is a slight structural cost but it earns its place by defining valid systemids values.

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 not be explained, and all 11 parameters are covered by the schema. The description supplies the missing operational context (which libraries are reachable and the systemids default), leaving only minor gaps such as pagination semantics.

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 every one of the 11 parameters is already documented, giving a baseline of 3. The description restates a few of those fields (title, author, publisher, NDC, systemids) but adds no syntax or format detail beyond the schema, so it does not raise the score.

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 gives a specific verb+resource ('図書館の蔵書を検索します' — searches the library collection) and enumerates the searchable fields (title, author, publisher, NDC). It implicitly distinguishes itself from search_libraries (which finds libraries) by focusing on holdings, but it never names or contrasts with a sibling tool explicitly.

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?

It supplies real usage guidance for the systemids parameter — the valid values, the ability to mix in school libraries, and that omitting it searches all libraries. However, it offers no explicit when-to-use-this-vs-alternatives guidance against get_ndc_info or search_libraries, so selection 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.