Search Japanese railway stations

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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false. The description adds behavioral context by stating it 'returns candidates' and explicitly says it does not silently resolve ambiguous inputs—this tells the agent to expect multiple results for ambiguous queries, which is not captured in annotations.

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 with zero waste: the first delivers the usage directive, the second describes behavior. It is front-loaded with the most important instruction and stays compact.

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?

Given the simple 2-parameter schema, annotations that cover safety, and an existing output schema (which defines return values), the description covers the essential ambiguity-handling behavior. It does not explain how to use the returned candidates (e.g., passing a station ID to search_trains), but that is adequately implied by the 'use before search_trains' directive. This is complete enough for an agent to invoke the tool correctly.

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 0%, so the description must compensate. It explains the query parameter implicitly as a station name in Japanese, English, or romanized form, but it never mentions the 'limit' parameter at all. Since limit is optional with a default, the omission is less critical, but for a tool with only two parameters, the description should clarify both to fully address parameter semantics.

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 returns station name candidates for Japanese, English, and romanized queries, and explicitly distinguishes it from the sibling search_trains by positioning it as a pre-step when no station ID is known. The verb 'Returns' and resource 'Japanese railway stations' give a precise purpose.

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?

'Use this before search_trains whenever no canonical station ID is known' gives an explicit when-to-use directive, and the note about not silently resolving ambiguous inputs (e.g., Osaka, Fukuoka) further clarifies the appropriate context. However, it does not explicitly state when to avoid this tool beyond 'when ID is known', which is implied but not explicitly framed as an exclusion.

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