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

With no annotations, the description carries the burden and does substantial work: it discloses per-call pricing ($0.005 USDC), the x402 payment mechanism and where the payment payload goes (_meta["x402/payment"]), and that sample=true caps results at 3 free rows. It does not describe response shape, error behavior, or rate limits beyond the limit/offset params.

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?

Front-loaded with identity and use cases, then the routes, then the payment/free-tier caveat — a sensible priority order. The route listing is dense shorthand but each clause is load-bearing; nothing is filler.

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?

Given a nested params object, no output schema, and no annotations, the description covers invocation and cost well but says nothing about what data comes back for each route (fields, row limits on paid calls, error responses for invalid codes). Enough to call it, not enough to fully predict its behavior.

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 coverage is 100%, so the baseline is 3, and the description adds real value beyond the schema by mapping which parameters belong to which route and marking lat/lon as required on /nearby. It still leaves parameter value formats (e.g. what 'type' accepts) to inference.

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?

States a concrete resource (airport data) and enumerates the three callable routes with their parameters, so an agent knows exactly what the tool exposes. It does not explicitly differentiate itself from sibling API tools, but the airport domain is unambiguous against siblings like colors, markets, or exchanges.

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 route list implies the selection rule: /nearby for lat/lon proximity, /search for query/country filters, /{code} for a direct lookup. The asterisk on lat/lon signals required parameters and the sample hint tells the agent how to try it without paying. No explicit exclusions or 'use X instead' guidance is given.

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