Alternative routes

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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, and the description adds real behavioral context: seat counts may be cached and should be confirmed with a search, and classes_listed is the API's raw count rather than bookable classes. It does not mention rate limits, result caps beyond 'up to 7', or freshness of prices beyond the caching note.

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?

Front-loaded with the core purpose, then organized by output section (with_one_change, nearby_*). It is dense and slightly run-on in the middle, but every sentence carries information; no filler.

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 an output schema present, the description need not enumerate return fields, yet it usefully explains what each section means and how to act on the ids. Coverage of caveats (cached seats, raw class counts) is good; a note on result freshness or pagination would make it complete.

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% for all three parameters, so origin/destination/date semantics are fully documented in the schema. The description adds no input-parameter detail of its own (its content is about output sections), 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 opening sentence states a specific purpose: finding alternative journeys (one-change trips, nearby train/bus/flight routes) when direct trains are full or expensive. The named result sections (with_one_change, nearby_*) make it easy to distinguish from mb_search_trains and mb_search_buses, which it explicitly points to as follow-ups.

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 clearly states the trigger condition ('when direct trains are full or dear') and routes the agent onward ('pass their ids to mb_search_trains, mb_search_buses or mb_search_flights'), plus a comparative hint that a direct bus may be cheaper/faster. There is no explicit statement of when *not* to use it (e.g., when a direct train exists and is available), so it falls just short of full routing guidance.

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