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

There are no annotations, so the description carries the full burden of behavioral disclosure. It does state what the tool returns ('nearby airports and common codes'), indicating a read-only lookup. However, it does not disclose behavior when the optional 'city' parameter is omitted (required params: 0), potential rate limits, or whether it prefers IATA over ICAO codes. This is a moderate gap for a simple lookup tool.

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 description is two sentences: 'Find airport IATA codes for a city.' then 'Returns nearby airports and common codes.' Every word earns its place, and it is front-loaded with the core purpose. No extraneous information or repetitive phrasing.

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 simple one-parameter tool with no output schema, the description gives the essential purpose and return type. However, it leaves ambiguity about the optional 'city' parameter—what happens if no city is provided? It also does not describe the format of the returned codes. These gaps prevent a higher score, though the overall simplicity keeps it adequate.

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?

The input schema has 100% description coverage with 'city' clearly described with examples. The tool description adds nothing semantically new beyond reiterating 'for a city'. Since schema coverage is high, the baseline is 3, and the description does not compensate with additional format details or edge-case handling.

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 clearly states a specific verb ('Find') and resource ('airport IATA codes') with a scope ('for a city'). It also mentions the output includes nearby airports and common codes, making it easily distinguishable from sibling tools like flight_search and cheapest_flights, which deal with flights rather than airport codes.

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?

The description provides clear context: it is for looking up airport IATA codes by city. Although it does not explicitly mention alternatives or 'when not to use', the sibling tool names (e.g., flight_search, price_calendar) make it obvious that this tool is specifically for airport code lookup, not flight search. This meets 'clear context, no exclusions'.

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