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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), so the bar is lower. The description still adds real value beyond them: the enumerated status outcomes (found, not_found, invalid, unavailable) and the conditional presence of owner_approved disclose response behavior the annotations cannot.

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, front-loaded with what the tool returns before detailing field semantics. The closing case/hyphen sentence duplicates the schema description, so it is not perfectly waste-free, but overall density is high.

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 naming each top-level field and explaining when owner_approved appears. For a one-parameter lookup, nothing an agent needs to call it correctly is missing.

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 coverage is 100% and the single 'tail' parameter is fully documented there. The description's note that case and hyphens are ignored merely repeats the schema's own wording, adding no new syntax or format guidance. Baseline 3 applies when the schema does all the work.

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 resource (one U.S. registration mark) and enumerates exactly what comes back (status, public_record, owner_approved), so the agent knows this is a single-aircraft lookup rather than a search. It never names search_aircraft explicitly, so sibling differentiation is inferred from the 'one registration mark' framing rather than stated.

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 implied by the singular 'one U.S. registration mark' scope, which contrasts naturally with the list-shaped search_aircraft sibling, but there is no explicit when-to-use or when-not-to-use guidance. Nothing tells the agent when to prefer check_availability or search_aircraft instead.

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