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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so safety is covered. The description adds real value beyond that by disclosing the required auth ('Needs the user's Cotlet API key with access to this app') and the shape of each result, which helps the agent plan ranking.

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, but the result fields are listed twice — once in the opening sentence ('times, duration, changes, operator and price') and again in the third sentence ('operator, departure and arrival, duration, number of changes and the lowest price'). That duplication costs space without adding information.

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?

No output schema exists, so the description usefully explains the return shape and the tool chaining to get_trip. Auth requirements are covered. It is nearly complete, only omitting round-trip/return_date and result-limit context that the schema carries.

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%, so all seven parameters are already documented. The description only reinforces a few of them (from/to, date, modes) and says nothing about limit, passengers or return_date, so it adds little beyond the schema — 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?

States a specific verb and resource (search trips between two places on a date) plus the modes covered (trains, buses, flights, ferries). It is clearly distinguishable from omio_get_trip and omio_list_bookings, which handle results and bookings respectively.

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?

Explicitly scopes the tool to 'one route and date' and routes the agent forward: 'Pass the trip_id of a result to get_trip for its fares.' No when-not guidance is given, but the intended workflow and alternative tool are clear.

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