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

Annotations already declare readOnly/non-destructive/non-open-world, so the safety profile is covered. The description adds genuinely useful behavior: the search corpus is only the already-loaded pages, excludes the wider internet, and excludes post-load updates, plus the explicit no-guessing fallback. It stops short of describing result ordering or matching semantics.

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 purpose and scope are front-loaded, and the later sentences about fallback behavior each carry instructions the agent needs. It is somewhat long for a one-parameter search tool, though nothing is purely redundant.

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 an output schema present, return values need no explanation, and the description covers scope limits, corpus freshness, and failure handling for a simple keyword search. The remaining gap is that it never relates itself to its five siblings, particularly the near-namesake `search_pages`.

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% for the single `query` parameter, so the schema already carries the semantics and the baseline of 3 applies. The description adds only a rephrasing strategy (expand abbreviations, try synonyms), which is guidance about querying rather than new meaning for the parameter itself.

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 (探す/search), resource (読み込んだページ/loaded pages from the named site), and return shape (抜粋と URL/excerpts with URLs), and it bounds the scope to the loaded pages of one site. What it never does is distinguish itself from the sibling `search_pages`, whose name suggests the same job.

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 gives explicit when-to-use guidance (質問されたらまずこれを使ってください) plus a fallback procedure: rephrase with expanded abbreviations or synonyms, and if still absent, tell the user the site does not cover it rather than guessing. Strong, but it names no sibling alternative, so the agent cannot route between `search`, `search_pages` and `fetch`.

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