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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, covering the safety and side-effect profile. The description adds useful behavioral context beyond these: the '28-day source cycle' (data freshness) and the 'technical evidence view' caveat, which clarify the scope and limitations. It does not contradict annotations, and the added context is meaningful.

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 with no fluff. It opens with the core action and source cycle, then lists the comparison dimensions, then gives usage examples and a caveat. It is front-loaded and every sentence contributes meaning, making it highly efficient and easy to parse.

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 must convey what the tool returns. It lists the compared dimensions, implying a structured comparison output, and states it is a 'technical evidence view,' which sets expectations. It doesn't explicitly mention the response_format parameter or output structure, but the schema covers that. For a moderate-complexity compare tool, this is largely complete, with only minor gaps in explicit return-value description.

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 both 'airports' and 'response_format' are already documented in the input schema. The description reinforces the 'two to eight' constraint for airports but does not add new syntax or format details beyond what the schema provides. Per the rubric, the baseline of 3 applies when the schema covers parameters, and the description offers only marginal additional semantic value.

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 explicitly states the verb 'Compare', the resource 'FAA NASR facilities', and enumerates the specific attributes compared (runway count/dimensions, hard-surface and lighted counts, ILS, etc.). It also provides concrete example queries ('compare JFK, LAX, and ORD runway capabilities') that clearly distinguish it from the single-airport profile and search siblings.

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 when-to-use examples ('Use this for...') and a clear when-not-to-use statement ('not an operational suitability decision or navigation source'). It also implies the alternative for single-airport queries by focusing on comparison, though it doesn't name sibling tools directly. This is strong guidance for an agent to decide when this tool is appropriate.

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