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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds one genuinely useful freshness detail ('Fares are the cheapest Aviasales travellers found in the last 48 hours; the live price is on the booking page'), but that concerns pricing rather than this lookup's behavior, and nothing is said about uniqueness of matches or result ordering.

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 lookup purpose is correctly front-loaded in the first sentence, but two of the three sentences are about fares and booking pages, which do not earn their place in a place-lookup definition and actively dilute the signal.

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 resolver with no output schema, the description should say what comes back (a place identifier/code and its metadata) and how it feeds the sibling tools; instead it spends its remaining budget on pricing minutiae, leaving the agent unsure what to do with the result.

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% for the single parameter 'q', including examples ('Lisbon or LIS'), so the schema carries the semantic load. The description adds no extra meaning about accepted input formats, ambiguity handling, or whether codes vs names behave differently, so the baseline 3 applies.

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 opening sentence gives a clear verb+resource ('Look up a city or airport code'), but the remaining sentences describe fare search behavior ('Cheap flights from any city', 'cheapest days to fly'), which does not match a resolver-style lookup tool and risks making the agent expect price results from this call. The purpose is stated but immediately muddied, and no differentiation from cheapest_dates or find_deals is offered.

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 statement of when to call this tool, no prerequisites, and no reference to the sibling tools cheapest_dates or find_deals that presumably consume the resolved code. The only implicit guidance is the sentence about fares, which points at the wrong usage.

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