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

Annotations already declare readOnlyHint=true, and the description adds meaningful behavioral context: it returns data for all counties, lists output fields, and notes updates are on source cadence. This goes beyond the annotations by describing scope and data refresh behavior, though it does not cover edge cases or data limitations.

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 structured with a clear first sentence stating the core output, a usage-guidance sentence, and an update note. It is slightly dense but every sentence earns its place; no filler. The length is appropriate for the information conveyed.

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?

For a simple read-only tool with no output schema, the description adequately covers the return value (including field names), scope (all US counties), usage context, and update cadence. Combined with the schema's parameter description and annotations, it leaves no major gaps for an agent to invoke the tool correctly.

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 a complete description of the optional 'days' parameter, including range, behavior (history series vs snapshot), and Gold tier requirement. With 100% schema coverage, the description adds no additional parameter semantics, so the baseline score of 3 is appropriate.

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 returns a 0-100 county airport-access score for all 3,222 US counties, with a detailed list of output fields. This is a specific verb (returns) and resource (airport-access score) that distinguishes it from sibling tools. The scope and metrics are unambiguous.

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 explicitly states when to use the tool: when the user asks about county proximity to commercial air service, travel accessibility, or site-selection decisions hinging on air access. It does not mention when not to use it or name alternative tools, so it falls short of a full 5, but the guidance is clear and context-rich.

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