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

Beyond the readOnly and idempotent annotations, the description discloses the exact response shape (same fields as search_empty_legs, with an enumerated list) and an important edge case: a not-available message if the flight is no longer published. This gives the agent useful expectations about the call's behavior.

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 description is three sentences, front-loads the core action, and every sentence earns its place: what it does, the returned fields, when to use it, and the stale-flight edge case. There is no redundant wording.

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 simple single-parameter read-only lookup with no output schema, the description is complete: it specifies the input, the return fields, the usage context, and the not-found behavior. Sibling tools and annotations cover the remaining context.

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?

The schema already documents flightId fully, including its source in the search_empty_legs result, and schema coverage is 100%. The description adds no new parameter meaning beyond saying 'by its id,' so the baseline score of 3 is appropriate.

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 uses a specific verb ('Look up') and a precise resource ('one empty leg flight by its id'), and it clearly distinguishes this tool from the sibling search_empty_legs by noting it returns the same fields for a single known flight. The purpose is unambiguous and differentiated.

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?

The description gives a clear use case: re-check a specific flight found earlier via search_empty_legs. It implies the alternative (use search_empty_legs for finding flights) by naming that sibling, though it does not explicitly state when not to use this tool or list all alternative tools.

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