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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely new behavior: the response envelope, the enumeration of status values (found, not_found, invalid, unavailable), and the conditional presence of owner_approved — all things annotations cannot convey. It does not contradict the readOnly hint.

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 the field-by-field breakdown. The reference to /{mark}/facts.json earns its place by telling an agent the payload matches a known document shape; the repetition of case/hyphen handling is the only wasted clause.

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?

There is no output schema, so the description carries the burden of explaining returns — and it does, enumerating the status values and the two payload branches including the conditional owner_approved field. For a single-parameter read tool this is close to complete, with only pagination/error-cadence details absent.

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 parameter is fully described in the schema, including the case and hyphen normalization. The description repeats that normalization verbatim rather than adding syntax, format, or failure-mode detail, so it is baseline value only.

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 resource (the public record for one U.S. registration mark) plus a distinct second payload (owner-approved facts), which an agent can separate from search_aircraft's multi-result behavior without opening either schema. It stops short of naming a sibling directly, so it is clear but not maximally 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?

Usage is implied by the singular 'one U.S. registration mark' framing, which signals a point lookup rather than a search, and the sibling search_aircraft makes that contrast inferable. However, there is no explicit when-to-use/when-not statement and no named alternative, so an agent must infer the routing.

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