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

The annotations already mark the tool as readOnly and openWorld, but the description adds valuable context: the $0.02 per call cost, the payment method (x402/MPP), and the ranking by real road drive time. It also clarifies that only scheduled-service airports are considered. No contradictions with annotations.

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 two sentences: the first front-loads cost and payment details, the second states the core functionality. It is concise and structured well, with no redundant phrasing, though the payment info could arguably be moved to a separate field.

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 has an output schema, so return values need no explanation. The description covers the main purpose, cost, payment, and ranking behavior. It doesn't mention error handling or rate limits, but for a simple query tool with readOnly annotations, this is sufficient.

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 schema already describes k, near, and airport_size; location lacks a description but has examples. The description adds a bit of meaning by calling location a 'named place' and noting 'scheduled service' for airport_size, but it does not significantly enhance understanding beyond the schema. With 75% coverage, the baseline is 3.

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 up to 5 airports with scheduled service nearest a named place, ranked by real road drive time, with IATA codes. This is a specific verb+resource and is distinctly different from sibling tools like drive_time or entity_lookup, making it easy for an agent to differentiate.

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 gives clear context on what the tool does (finding nearest airports) but does not explicitly mention when not to use it or name alternatives. However, the uniqueness of the functionality (airport location) makes usage intent obvious, so no exclusions are needed.

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