Search direct Shinkansen trains

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

Annotations already cover read-only, idempotent, non-destructive behavior, so the description adds value with non-trivial behavioral detail: filters are applied before pagination and only direct services are returned. No contradiction with the 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 contain the prerequisite, core scope, required input, and filter/pagination behavior with no filler. The most important usage constraint is front-loaded.

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 description is nearly complete for a read-only search tool: it covers prerequisites, scope, required date, optional filters, and filter-pagination ordering, while the output schema covers return details. It could be slightly stronger by naming the sibling for transfer journeys.

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?

With schema description coverage at only 22%, the description must compensate. It groups optional filters into 'time, service, and operator' and notes they apply before pagination, but it does not map them to departureAfter/departureBefore, serviceTypes, and operators or explain their value 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 states a specific verb and resource: 'Searches direct Shinkansen services only, never transfer journeys.' This clearly identifies the tool's scope and semantically differentiates it from transfer-search siblings such as search_journeys.

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 sequencing ('Use after resolving both station IDs') and a clear exclusion ('never transfer journeys'), plus a required date. It does not name an alternative tool for transfer searches, so it falls just short of fully explicit sibling routing.

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