cheapest_per_day

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

No annotations are present, so the description must carry the full burden. It explicitly states that days with no flight or price return 'price=None', which is a key behavioral detail. It also specifies the month parameter format. However, it does not disclose potential costs, rate limits, or authentication requirements, leaving some gaps for a tool with no annotations.

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 three sentences long, with each sentence serving a clear purpose: stating the tool's function, clarifying the month parameter format, and explaining behavior for missing prices. There is no redundant or irrelevant information, making it highly concise and well-structured.

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?

Given the presence of an output schema (not shown but indicated), the description does not need to explain return values. It covers the main use case, the month parameter format, and the behavior for missing data. It could mention potential constraints like maximum date range, but overall it is complete for a simple tool with a limited scope.

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 0%, so the description must compensate. It adds meaning for the month parameter by specifying the ISO format (YYYY-MM-01). For origin and destination, it only provides an example (DUB->BCN) and mentions 'one route', but does not explicitly state that they should be airport codes or expected format. This is partial compensation.

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 that the tool provides the cheapest fare per day for one route across a single calendar month, using specific verbs ('cheapest fare per day') and a resource ('one route'). It distinguishes itself from sibling tools (explore_destinations, find_anywhere_under, find_flights) by focusing on a fixed-route monthly calendar view, as evidenced by the example 'what's the cheapest day in July to fly DUB->BCN'.

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?

The description provides a concrete use case example ('powers ... style prompts'), which implies the intended scenario. However, it does not explicitly mention when not to use the tool or directly compare it to sibling tools. The example is sufficient to guide usage, but lacks explicit exclusions or alternatives.

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