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

Annotations already declare read-only, idempotent, non-destructive, open-world behavior, yet the description adds real value by distinguishing two outcomes that annotations cannot: an airfield with no frequencies returns an empty list with found:true, while an unrecognized code is refused with a clear error. It also sketches the return shape (type, human description, MHz) in the absence of an output schema.

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?

Four short sentences, front-loaded with the resource and payload, followed by input routing and then the two edge-case outcomes. No filler, and the most decision-relevant facts come first.

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 one parameter, no output schema, and annotations already covering the safety profile, the description fills the remaining gaps: what a result contains, what an empty result means, and how failures are signaled. Nothing an agent needs to call or interpret this tool 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%, so the single code parameter is already documented with format examples. The description still adds meaning by widening the accepted input universe to whatever ourairports_lookup accepts, which the schema's ICAO/IATA/GPS/local enumeration does not state as a rule.

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 resource (radio frequencies for one airfield) plus the source dataset and the exact fields returned (type, description, MHz), with the frequency-type enumeration making the scope unambiguous. Siblings airport_navaids and airport_runways are implicitly distinguished by the resource named, so an agent can pick correctly without opening schemas.

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?

"Pass any code ourairports_lookup accepts" explicitly ties input handling to a sibling tool, giving the agent a resolution path. It does not explicitly say when to prefer this over airport_navaids or airport_runways, but the resource split is clear enough that no exclusion clause is needed.

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