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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety needs no restating. The description adds genuinely new behavioral context: the unit of the returned values (MHz) and the metered pricing model with its daily allowance and per-call charge, which annotations cannot express. It stops short of describing result shape or rate-limit behavior beyond price.

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?

Two tight sentences: the resource and its unit come first, the billing condition second. No filler, no repetition of the title, and nothing an agent must read past to find the core meaning.

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?

The tool is simple (one required identifier), an output schema exists so return values need not be documented, and annotations carry the safety profile. Pricing and unit are disclosed, leaving only minor gaps like whether multiple frequencies are returned or how results are ordered.

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?

With a single parameter and 100% schema description coverage, the schema already explains that code accepts ICAO (EGLL), IATA (LHR) or an OurAirports ident. The description adds nothing about the identifier parameter, so the baseline 3 for schema-covered parameters applies.

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?

Names the resource precisely (an airport's radio frequencies) and enumerates the concrete channel types (tower, ground, ATIS, approach), which distinguishes it from sibling tools like airports__runways or airports__navaids-near. The retrieval verb is implicit rather than stated, but the resource and scope 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 never says when to reach for this tool versus airports__airport, airports__runways, or the other airport siblings. The only conditional language concerns billing (free within the daily allowance, then $0.001 USDC), which is cost information, not usage guidance.

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