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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true. The description adds genuine value beyond them by explaining the domain semantics of 'exchangeable' and 'refundable' and by disclosing an auth requirement ('Needs the user's Cotlet API key with access to this app').

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 purpose is front-loaded, but the first two sentences restate the same idea ('Legs of one trip and its fare options...' then 'Returns the legs of one search result and every fare option for it...'), which is redundant and inflates length.

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 no output schema, the description does the necessary work of describing the return payload (legs, fare options, price, conditions) and mentions the API-key requirement. It is complete enough to call the tool correctly, with only the missing when-to-use routing as a gap.

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 a single documented trip_id parameter, so the schema carries the parameter meaning. The description references fare_id, but that is an output/booking concept rather than an input parameter, so it adds little to parameter understanding beyond the baseline.

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 names a specific verb+resource ('Returns the legs of one search result and every fare option for it with the price and its conditions'), which clearly scopes it as a read of a trip's legs/fares. It implicitly separates itself from omio_get_booking by tying the input to a search result, though it never names that sibling explicitly.

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?

'Pass fare_id to book_trip' gives useful next-step guidance, placing the tool in the search_trips -> get_trip -> book_trip flow. However, it never states when to use this versus omio_get_booking or omio_get_tickets, leaving the selection to inference.

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