get_popular_directions

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds the result shape (cities plus a fare) and the direction semantics (origins into the destination), which is real value beyond annotations, but it says nothing about rate limits, locale/currency defaults, or result volume.

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?

Two short paragraphs; the capability statement is front-loaded and the routing guidance follows with zero filler sentences.

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?

With an output schema present, return values need no explanation, and the description plus annotations and full schema coverage give everything an agent needs to select and invoke it correctly.

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%, including the required IATA code and locale/currency defaults, so the schema carries the parameter burden. The description only reiterates that the request is keyed on the destination, adding no format or syntax detail beyond the schema.

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+resource: lists origin cities for flights into a destination, with fares. It explicitly distinguishes itself from get_city_directions and search_flights, so the agent can route correctly without opening schemas.

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?

States when to use it ('where travellers reach a city from and what that costs'), the keying ('the request is keyed on the destination'), and names two alternatives with the condition that selects each ('where someone can fly from a city' vs 'prices on one known route').

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