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

Annotations already state readOnly and openWorld, but the description adds substantial non-annotation behavior: $0.002 USDC per successful call via x402, failed calls uncharged, coverage limited to large/medium and IATA-coded airports, and explicitly no time zone. These are decision-relevant constraints beyond structured 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?

The description is packed into a few front-loaded clauses: resource, lookup modes, coverage caveats, returned fields, and pricing. Every sentence carries useful information without 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 an output schema, readOnly/openWorld annotations, and full schema descriptions, the description supplies the remaining decision-critical facts: source, coverage exclusions, missing time zone, and x402 pricing. Nothing essential for correct invocation is missing.

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% and documents all six parameters including code, q, lat/lon, limit, and radiusKm. The description only echoes that q is name/city words and radius is up to 300 km, both already in the schema; baseline 3 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?

States a specific verb ('Airport lookup') and resource ('OurAirports extract'), enumerates the three lookup modes, and names returned fields. The airport-specific scope naturally distinguishes it from general geocoding/places siblings.

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?

It clearly explains the supported query modes (code, name/city words, nearest within radius) and coverage limits, but never names alternatives such as geocode, places, or flights. The agent must infer when to choose this tool over those siblings.

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