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

The annotations already establish that this is a read-only, open-world, non-destructive lookup. The description usefully adds the 2-credit cost, the 29,000-facility scale, and the distinction between base lookups and paid-plan fields, but it is ambiguous about whether premium fields such as coordinates and timezones are available in the current call or only under a paid plan.

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 core purpose is front-loaded, but the description redundantly repeats 'Airports Lookup' at the start. The second sentence is a dense marketing-style list of paid features, which adds useful scope information but also includes details that are not directly actionable for invoking the tool.

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 an output schema, full parameter descriptions, and annotations present, the description covers enough to understand the basic lookup. However, it leaves gaps around sibling selection and whether paid-plan fields affect current results, so it is adequate but not fully complete for this 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?

Schema coverage is 100%, so the five parameters are already documented in the input schema. The description names the main lookup dimensions, but it does not clarify precedence or valid combinations, and its mention of states and country names goes beyond the schema's actual country-code parameter while the paid-plan wording muddies whether ICAO, name, and city parameters are currently usable.

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 gives a specific verb and resource: it 'resolves 3-letter IATA codes into official airport names' and can match ICAO codes, cities, states, and country data. It is clear that this is an airport-data lookup over 29,000 facilities, though it does not explicitly distinguish itself from close siblings such as AirportCodeConverter.

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?

There is no explicit guidance on when to use this tool versus alternatives like AirportCodeConverter, AirlineLookup, or CitiesLookup. The mention of paid-plan features adds context about data coverage but does not tell an agent when this lookup is the right choice or when it should not be used.

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