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 non-obvious behavioral facts beyond that: private owners are withheld from registration records, and foreign aircraft return no record but may still have live position data. It doesn't mention rate limits or result caps for word searches, which is the remaining gap.

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?

Front-loaded with the input formats, then the return shapes, then the foreign-aircraft caveat, then attribution — a sensible information order with no filler sentences. It is dense and backtick-heavy, which makes it slightly harder to scan than a plainer phrasing would, but nothing 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?

With no output schema, the description carries the return-value burden and does so: it enumerates the fields in `record` (maker, model, year, seats, engines, airworthiness, status, expiry, hex) and in `live` (lat, lon, altitude, speed, squawk), plus what `matches` means. Combined with input formats and the foreign-aircraft edge case, an agent has everything needed to call it and interpret the reply.

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 the schema already documents it at 100% coverage, so baseline is 3. The description adds concrete format examples per input mode (N172SP / 172SP, A2D8E1, UAL1895, 'Cessna 172') that clarify how the same string is interpreted differently, which is real added meaning beyond the schema's single example.

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+resource (look up an aircraft) and enumerates the accepted identifiers (N-number, Mode S hex, callsign, free-text register words). The resource is unmistakably distinct from the sibling lookups for satellites, ships, trains and vulns, so an agent can select it without opening the 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?

It gives clear selection context by naming the three result modes — `record` for FAA registration data, `live` for current ADS-B position, `matches` when words are supplied — which effectively tells the agent what kind of query yields what. It stops short of naming alternatives or exclusions (e.g., when to prefer a different NicheDB tool), so it lands at a clear-context 4 rather than a full 5.

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