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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false, and destructiveHint=false, so the safety profile is fully covered elsewhere. The description adds value by disclosing the shape of the returned record (name, city, country, kind), but says nothing about behavior when a code is not found or about what values 'kind' can take — a real ambiguity given IATA codes span both airlines and airports.

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?

One short sentence with zero filler; the key information (single code, return fields) is front-loaded. It is clipped to the point of slight vagueness, since 'kind' is undefined terminology, but nothing is wasted.

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 one-parameter read lookup with strong annotation coverage and no output schema, the description is close to sufficient — it explains what the record contains. However, it omits not-found behavior and the meaning of 'kind', and gives no signal about when this lookup is preferred over get_airport or search_iata, which is the main gap for an agent navigating this large 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 description coverage is 100%: the single 'code' parameter is documented with a regex pattern and an example ('DEN'). The description's '3-letter code' merely restates the schema constraint, adding no syntax or formatting information beyond it. Baseline 3 applies when the schema does the heavy lifting.

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 names a specific resource ('the reference entry for a single 3-letter code') and enumerates the returned fields (full name, city, country, kind), so an agent knows exactly what comes back. It is a noun phrase rather than a verb phrase, and it never distinguishes itself from close siblings like get_airport, search_iata, or list_airports, so an agent cannot tell from the description alone which one to call.

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 when-to-use guidance, no exclusions, and no named alternative. With siblings get_airport, search_iata, and list_airports all plausibly handling airport/code lookups, the description leaves the routing decision entirely to inference.

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