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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, so safety profile is covered. The description adds valuable behavioral context beyond annotations: it explains that the response and widget UI are localized based on the inferred language, and that currency defaults are derived from locale. This enriches the agent's understanding of dynamic behavior.

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 relatively concise and front-loaded with the main function. It includes a few multilingual examples which, while useful, add length. Overall, every sentence contributes value without unnecessary fluff.

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 tool's complexity (7 params, no output schema), the description provides sufficient context for correct invocation: route, month, language inference, currency defaults, and one-way/round-trip behavior. It does not describe the output format in detail, but this is partially mitigated by good parameter documentation and annotations.

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%, so parameters are already well-documented. The description adds some emphasis on the locale parameter (MUST infer) and explains currency defaults, which are also in the schema. It does not significantly expand on parameter semantics beyond what the schema provides, hence the baseline 3.

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 identifies the tool as a price calendar for a given route returning cheapest daily prices across a full month. It uses a specific verb ('returns'), specifies the resource ('cheapest daily price'), and clearly distinguishes from siblings like search_flights and flight_details by focusing on month-level flexibility and cheapest days.

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?

Provides explicit usage guidance with clear examples ('when the user shows date flexibility', 'cheap days', 'flexible travel windows') and sample queries in multiple languages. However, it does not explicitly mention when not to use this tool or alternative tools, so it falls short of a 5 but is clearly above a 3.

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