transit_alternative_routes

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

Annotations already declare readOnlyHint=true, so the safe-read behavior is known. The description adds value by disclosing that routes are ranked and delay-aware, but it does not explain how rankings are computed, data sources, or response structure. This is comparable to the get_calls example and merits a 3.

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 a single, focused sentence that front-loads the action and key qualifiers ('delay-aware,' 'ranked'). Every word contributes meaning without redundancy or fluff.

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?

With only two required string parameters, high schema coverage, and no output schema, the description provides sufficient context for an agent to invoke the tool. It implies the return is a ranked list of routes, which covers the primary output need, though it omits details on result format or data freshness.

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 100% with clear definitions for 'from' and 'to' (origin and destination station names). The description does not add additional parameter-level meaning, so the baseline 3 applies.

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 uses a specific verb ('Suggest') with a clear resource ('alternative routes for Japanese train travel') and adds differentiating details like 'delay-aware' and 'ranked routes that avoid currently-disrupted lines.' This clearly distinguishes it from sibling tools such as transit_route_plan, which presumably provides standard route planning.

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 implies usage context by noting routes avoid 'currently-disrupted lines' and are 'delay-aware,' which signals when this tool is appropriate. However, it does not explicitly mention when not to use it or name alternatives like transit_route_plan, so it falls short of a 5.

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