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

Annotations already declare readOnly/idempotent/non-destructive/open-world, so the safety profile is covered. The description adds genuinely non-structured behavior: unknown codes produce a clear error rather than an empty success, and it enumerates the returned field set despite having no output schema.

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 purpose and scope in the first clause, then code formats, then return values, then the alternative. Dense with parentheticals and examples, which is slightly heavy but each clause carries information an agent needs.

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 single-parameter read tool with no output schema, the description covers input formats, output fields, error semantics, and the alternative tool. The only gap is not disambiguating against ourairports_search / search_airports, which matters in this crowded sibling set.

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 parameter description already lists ICAO/IATA/GPS/local ident, so the bar is a baseline 3. The description earns a bump by restating the accepted code families with richer worked examples and by noting the local/national ident case (e.g., '00A', 'AT-0001') that agents commonly get wrong.

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 ANY airfield in the OurAirports bulk dataset') and scopes it precisely (~86,000 rows, all airport types including those without IATA codes). It also explicitly positions itself against the sibling get_airport / AirportGap data, so an agent can distinguish the two without opening schemas.

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?

Gives an explicit routing rule: use this when get_airport's AirportGap data does not recognize a code, or for heliports/seaplane bases/ICAO-only fields. It does not address the other nearby sibling, ourairports_search, so the code-lookup vs name-search choice is left implicit.

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