Search transfer journeys

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

Annotations already cover read-only, idempotent, open-world, and non-destructive behavior. The description adds a valuable behavioral detail beyond those: the Shinkansen-first provider reports journey search as unsupported instead of incorrectly returning direct trains. This helps agents interpret empty or error responses correctly.

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 deliver the core usage rule and a provider-specific caveat with no filler. The most important guidance is front-loaded, making the description easy to scan and act on.

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 selection context is strong and the output schema covers return values, but the tool has 8 parameters with only 25% schema coverage. The description does not compensate for that gap, leaving several parameter semantics unexplained for correct invocation.

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 only 25%, covering just fromStationId and toStationId. The description provides no explanation of operators, serviceTypes, includeNonShinkansen, departureAfter, or departureBefore, so an agent has little guidance for correctly setting most parameters.

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, actionable rule: use this tool for routes that may include transfers, not for an individual train. This clearly separates it from search_trains and other sibling tools. The provider caveat reinforces the tool's unique role rather than blurring it.

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 (routes with transfers) and an explicit when-not-to-use boundary (not for an individual train). It does not name search_trains as the alternative, but the exclusion is strong enough that an agent can infer the correct routing.

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