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

Annotations already cover the read-only, idempotent, non-destructive profile, so the bar is lower. The description adds real value beyond them: it declares that results reflect data 'as currently published', that an unpublished flight yields a not-available message rather than an error, and that price is whole-aircraft with taxes/fees deferred to checkout. Auth and rate-limit behavior remain unstated, keeping it out of the top band.

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?

Two sentences, no filler. The action and scope lead, and the fallback behavior follows. Every clause carries information the agent needs.

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 carries the return-value burden and does so by enumerating route, departure time, price, aircraft type, seats, amenities, and booking link, plus the negative case. It is nearly complete; the only minor gap is that it doesn't distinguish a not-found id from an unpublished flight.

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?

Only one parameter and schema description coverage is 100%, so the schema already defines flightId and its provenance. The description's 'by its id' adds no syntax, format, or validation detail beyond that. 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 ('look up') and resource ('one empty leg flight by its id'), and the singular-by-id scope cleanly separates it from the sibling search_empty_legs, which returns listings. An agent can route between the two without opening either schema.

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?

Usage is only implied: the agent is expected to have a flightId already, which is hinted at by the schema ('as given in the flightId field of a flight listing') but never stated in the description. No alternatives (search_empty_legs, request_booking) or when-not conditions are named.

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