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

Annotations already cover safety (readOnlyHint, idempotentHint, destructiveHint). The description adds that the tool returns a monthly matrix grouped by transfers, which is beyond the annotations, and includes a usage example. However, it does not disclose rate limits, authentication nuances (beyond the _apiKey parameter), or any details about empty results or error handling. This is modest but acceptable given the annotation coverage.

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 a single sentence that clearly states the verb and resource, followed by an example call. It is front-loaded with the core purpose and wastes no words. The inline example is compact and helpful, contributing to an efficient, well-structured definition.

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?

There is no output schema, so the description should clarify the return format. It only says 'month matrix' without defining the structure, and it does not specify behavior when the optional month parameter is omitted. There is no mention of error handling, empty results, or API limitations. For a tool with five parameters and no output schema, this is a noticeable gap, though the example provides some practical guidance.

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 full coverage (100%) with descriptions for all five parameters, including format examples for month and IATA codes. The description does not add meaning beyond what the schema already provides; it merely repeats the IATA requirement and offers an example call. With high schema coverage, the baseline is 3, and the description does not elevate it.

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 purpose: it retrieves the cheapest ticket price for each day of a month, grouped by number of transfers, and labels this a 'month matrix'. It also specifies the use of IATA city/airport codes and provides a concrete example. While it does not explicitly differentiate from sibling tools like travelpayouts_price_calendar, the name and the specific output description make the purpose distinct and actionable.

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 offers no guidance on when to use this tool versus the other travelpayouts tools (e.g., travelpayouts_price_calendar, travelpayouts_cheap_prices). It does not mention scenarios, alternatives, or exclusions. An agent would have to infer usage solely from the name and description, which is insufficient.

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