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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds valuable context beyond that by disclosing the billing model (free daily allowance, then per-call x402 charge) and enumerating returned fields.

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 compact sentences, front-loaded with the returned data before the pricing note. No waste, though the pricing clause is somewhat tangential to describing the resource.

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?

With an output schema present, return values need no further explanation. The description covers what the tool returns and its cost model; the main gap is the absence of guidance on choosing it over sibling airport tools.

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%: the single 'code' parameter is fully documented as accepting ICAO, IATA or OurAirports identifiers. The description adds nothing about the parameter, so the baseline 3 is appropriate given the schema carries the burden.

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 resource and its returned attributes: runway length, width, surface, lighting and each end's identifier, heading and elevation. It distinguishes itself from siblings like airports__airport and airports__frequencies by focusing on runways, though it never explicitly contrasts itself with them.

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?

There is no when-to-use guidance. The only contextual detail is pricing ('Free within the daily allowance, then $0.001 USDC per call via x402'), which tells the agent about cost but not when to choose this tool over siblings like airports__airport or airports__near.

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