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

Annotations already declare readOnly, idempotent, and non-open-world, so the safety profile is covered. The description adds real behavioral context beyond that: it explains the resolution granularity (one airport vs. all airports in a city) and that the returned code is meant to be fed into origin/destination fields. It stops short of describing result size or fallback behavior on no match.

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?

Three compact sentences, front-loaded with the usage trigger, then the behavior, then the exclusion. No filler and nothing redundant with structured fields.

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?

Although an output schema exists (so return shape needn't be documented), the description still conveys the practical payload semantics an agent needs: the code to use, and the airport set a city code covers. With fully documented params and annotations, nothing essential is missing.

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 baseline is 3, and the description goes beyond it by clarifying that 'query' accepts a place name or a code and by describing how the query is interpreted (single airport, whole city, or code-to-coverage). It adds meaning not present in the schema's field titles.

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 and resource ('matches a place name or code') and the concrete output ('returns the code to pass as origin or destination'), which cleanly separates it from siblings like flight_lookup and search_flights. An agent can identify its role 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?

Explicitly says when to use it ('before searching' when unsure of a code) and when not to ('Not needed for well-known codes like JFK or LHR'), with a concrete example. This is close to ideal routing guidance for a lookup/resolution tool.

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