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

Annotations already cover the safety profile (readOnlyHint, openWorldHint, idempotentHint=false), and the description adds genuinely new behavioral context: cost ($0.02 per call), the payment mechanisms (x402/USDC on Base via _meta, MPP on the HTTP URL), and that ranking is by real road drive time rather than straight-line distance.

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?

Compact and front-loaded with the pricing/payment constraint, then the functional summary. Payment detail consumes a large share of the text, but every sentence carries actionable information.

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 not be described. The description covers purpose, cost, payment path, and ranking basis adequately; only the disambiguation hint (`near`) is left entirely to the schema.

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 75%, so the schema already carries most parameter meaning (k, near, airport_size all documented there). The description reinforces the k cap ('Up to 5'), the place input, and the scheduled-service filter but adds little syntax or format detail beyond the schema.

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 specific verb+resource: returns up to 5 airports with scheduled service nearest a named place, ranked by real road drive time, with IATA codes. This clearly separates it from generic siblings like drive_time or drive_matrix, though it never explicitly names an alternative.

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?

Usage is implied by 'nearest a named place' and the airport-size constraint, and it discloses the paid-access requirement. However, it gives no explicit when-to-use/when-not guidance or routing to a sibling tool.

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