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

Beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true), the description discloses real behavior: per-call confirmation is on by default and can be switched off, the action 'reaches other people' so the user must confirm, and it requires a Cotlet API key with access to this app. It does not clarify irreversibility or what happens to the canceled itinerary post-refund.

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 requirement to cancel either a refundable fare or an Omio Flex booking is stated twice ('Cancel a refundable booking, or one with Omio Flex' and again 'Cancels one booking that Omio lets you cancel online: a refundable fare, or a booking with Omio Flex'). The confirmation info is front-loaded reasonably, but a third of the text is redundant.

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?

For a single-parameter mutation tool with no output schema, the description covers eligibility, refund source, confirmation behavior, and auth requirements. The main remaining gap is what the response contains and whether cancellation is reversible.

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% and there is only one parameter, whose description ('Booking ID from list_bookings') is already in the schema. The prose adds no new syntax, format, or sourcing detail beyond the structured field, 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 states a specific verb and resource ('Cancel a refundable booking, or one with Omio Flex') and even names the scope limit (only bookings Omio lets you cancel online). It does not explicitly name or contrast against sibling tools like omio_change_booking or omio_get_cancellation_quote, so it falls short of the top score.

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 clear eligibility conditions for when this tool applies (refundable fare, or a booking with Omio Flex) and points to get_cancellation_quote as the source of the refund amount. It stops short of explicit when-not guidance, e.g. naming omio_change_booking as the alternative when the user wants different dates rather than a cancellation.

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