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

Annotations already declare read-only, idempotent, non-destructive behavior, and the description goes further by disclosing two non-obvious outcomes: sparse coverage yields an empty list with found:true, while an unrecognized code is refused with an error rather than a false success. That is exactly the kind of context annotations cannot carry.

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?

Three tight sentences: what it returns, how to call it, and the two edge-case outcomes. The resource definition is front-loaded and no sentence 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?

With no output schema, the description compensates by enumerating returned fields (ident, name, type, frequency, coordinates, elevation, DME channel, power) and covering both the empty-result and error paths. An agent has everything needed to call and interpret it.

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 already documents the single code parameter as ICAO/IATA/GPS/local. The description reinforces this by tying accepted values to the sibling lookup tool's code universe, adding a small amount of cross-tool meaning 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 resource (navigational aids for a single airfield), enumerates the aid types and the returned fields, and pins the scope to 'one airfield', which cleanly separates it from the airport-level siblings like airport_frequencies and airport_runways.

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?

Tells the agent that any code ourairports_lookup accepts works here, and explicitly sets expectations that most airfields return an empty list rather than an error. It never names an alternative tool to use instead, so it falls just short of full when/when-not/alternatives coverage.

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