駅の時刻表

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It reveals a non-obvious behavior: ambiguous line/direction leads to an error containing a candidate list, prompting the user to refine. It does not mention rate limits or return format, but for a read-only timetable lookup, the disclosed ambiguity handling adds meaningful insight.

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 concise, consisting of two sentences. The first sentence states the core purpose, and the second explains the error-handling behavior. There is no redundant or extraneous information, and the structure is front-loaded with the main action.

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?

The tool has no output schema and no annotations, so the description must provide sufficient context. It covers the core function and the key ambiguity error behavior. The schema itself references search_station for station codes, which mitigates the need for the description to do so. Overall, it is fairly complete for a straightforward retrieval tool.

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 has 100% description coverage for all six parameters, including examples and enums. The description adds no additional parameter-specific semantics beyond restating station/line/direction as the main selectors. Since the schema already documents parameters thoroughly, the baseline score of 3 is appropriate.

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 it retrieves departure timetables for a specified station, line, and direction. This is distinct from the sibling tools (search_station, search_route, get_train_status). The verb '取得する' and resource '発車時刻表' are specific and unambiguous.

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 provides clear context for when to use the tool: obtaining timetables with optional line/direction filtering. It also instructs the user to refine and retry when ambiguous line/direction causes an error. However, it does not explicitly mention when not to use this tool or compare it to alternatives.

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