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

With no annotations, the description carries full responsibility for disclosing behavior. It usefully reveals that booking links include a Travelpayouts referral code and that prices are identical with or without it. However, it does not explain what the response contains, how results are ordered, or other operational side effects.

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 description is compact and front-loaded with the core purpose, followed by the important referral-code disclosure. The PT/EN duplication is somewhat redundant but justifiable for bilingual users and does not bloat the text.

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?

The parameters are well documented by the schema, and the description implies the tool returns booking links. Still, with no output schema, it would be helpful to state what fields are returned, whether results are sorted by price, and how optional return_date affects the search. Some operational details remain implicit.

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?

The schema already covers 100% of parameters, so the baseline is 3. The description only restates the existing 'place name in Portuguese' behavior for origin and destination, adding no new semantic 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?

The description clearly states the tool's function: finding the lowest known price between two points with flexible dates. It also adds distinguishing context by noting it accepts Portuguese place names, though it does not explicitly contrast itself with the sibling tools.

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 guidance on when to use this tool versus search_flights or price_calendar. The phrase 'flexible dates' hints at a use case, but no explicit conditions, exclusions, or alternative tool recommendations are given.

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