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

With no annotations, the description carries the disclosure burden. It reveals that results include excerpts ('抜粋つきで'), that the search is scoped to Yomitasu pages, and that it can also surface introduction pages but not full site content. It doesn't explicitly state read-only behavior, but 'search' strongly implies it, and the corpus boundary is well articulated.

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 with no wasted words. The purpose is front-loaded, followed by a concrete list of searchable topics, and then usage guidance with an exclusion. Every sentence earns its place and the overall length is appropriate for the information conveyed.

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 search tool with two simple parameters and no output schema, the description covers the essential context: what is searched, what the output looks like (excerpts), when to use it, and what it should not be used for. It doesn't detail return fields or pagination behavior, but those are reasonable gaps given the schema's default values and the tool's simplicity.

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 50%: the query parameter is documented with an example, while limit has no schema description. The description reinforces the query semantics by explaining that it finds passages matching words, but it adds no meaning for the limit parameter beyond what the schema provides. This is adequate but not compensatory.

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 opens with a specific verb and resource: searching Yomitasu pages for matching passages with excerpts. It enumerates concrete searchable topics (pricing, FAQ, terms, etc.) and explicitly distinguishes its scope from searching within individual registered sites, which are delegated to site-specific MCP servers. This clearly differentiates it from sibling tools like get_page and list_pages.

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 gives an explicit when-to-use instruction: 'ヨミタスについて質問されたら、まずこれを使ってください' (use this first when asked about Yomitasu). It also provides a clear exclusion: site introduction pages can be found here, but content inside those sites should be checked with that site's MCP server. This effectively routes the agent to the correct alternative.

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