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

No annotations, so the description carries the full burden; it discloses the key behavioral trait that results are limited to origins with cached priced calendars and that counts reflect priced destinations. It does not cover cache staleness/refresh behavior or whether the list is exhaustive, so it falls short of full disclosure.

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 short sentences, each earning its place: return shape first, then the routing guidance to each sibling. Nothing is redundant or buried.

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?

No parameters, no output schema, no annotations — the description must and does explain both the returned content (origins plus per-origin counts) and how it relates to the sibling tools, which is everything an agent needs to invoke and interpret it.

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?

Zero parameters, so the baseline of 4 applies; there is no parameter semantics to explain and the description correctly avoids inventing any.

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?

Specific verb and resource ('Returns the departure airports (IATA)') plus precise scope ('that have at least one priced weekend calendar') and the returned payload ('count of priced destinations per origin'). An agent can distinguish this from both siblings without opening any 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 routes the agent: 'Start here to learn what cheapest_weekends can answer at once' names the primary use case, and 'weekend_prices works for any airport pair and searches live when needed' supplies the fallback condition when an origin is not listed. Both alternatives and their selecting conditions are stated rather than inferred.

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