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

Annotations are absent, so the description carries the full burden of disclosing behavior. It does not mention any side effects, limitations (e.g., date range flexibility window, result count), authentication requirements, or error handling. It only states the output in simple terms. This is insufficient for a tool with no structured behavior 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 exceptionally concise: two sentences, with the core purpose front-loaded. Every clause adds value—the output format and the usage intent are both included without redundancy. No filler words or unnecessary details.

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 9 parameters and no output schema or annotations, the description provides only minimal context. It explains the tool's purpose and output format but omits details like the flexibility window size, whether results are limited in number, or how the 'around' date is determined. It is sufficient for a basic understanding but leaves key operational details unaddressed.

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 input schema provides 100% coverage with descriptions for all 9 parameters, so the baseline is 3. The description adds a general context of 'one-way fares' and 'around a chosen departure,' but does not elaborate on any specific parameter semantics beyond what the schema already states.

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 a specific action ('Generate a flexible calendar'), the resource ('lowest one-way fares around a chosen departure'), and the output format ('date → cheapest-price entries'). It also includes a usage intent ('to help pick the best day to fly') that distinguishes it from exact itinerary searches. The phrasing 'not exact itinerary selection' differentiates it from sibling tools like flights_search.

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 clear usage context—'flexible-date price discovery'—and explicitly states a limitation: 'not exact itinerary selection.' This tells the agent when to use the tool and hints at alternatives (exact search tools) without naming them. It lacks explicit 'when not to use' instructions beyond the one exclusion, so it's not quite a 5.

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