駅検索（駅コード・路線一覧）

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

With no annotations, the description carries the full burden. It discloses that station codes are returned, and additional route/direction info with groupId is only returned when the candidate narrows to one. However, it does not explain behavior for multiple or zero matches.

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?

Two sentences, no redundancy, front-loaded with the primary purpose and followed by the conditional behavior and usage context. Every sentence earns its place.

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 simple one-parameter tool with no output schema, the description covers the purpose, conditional behavior, and usage context. It could be improved by describing the response format for multiple candidates, but it is largely complete.

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 schema already fully describes the query parameter with an example ('駅名（例: 新宿）'), and the description does not add significant new information about parameter syntax or format. Per the rubric, high schema coverage (100%) yields a baseline of 3.

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 clearly states the tool's purpose: searching for station codes from station names. It also specifies the conditional return of route/direction lists with groupId, distinguishing it from sibling tools like search_route and get_timetable.

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 explicitly states that this tool is used as a pre-stage for get_timetable, providing clear usage context. It does not explicitly exclude alternatives like search_route, but the role is obvious enough.

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