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

Annotations declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, which cover the safety profile. The description adds that the tool returns a found flag and aircraft object, which is useful behavioral information. It does not mention limitations like whether it requires a connection or what happens when no aircraft is found, but with annotations covering safety and the description covering return format, it is adequate.

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 a single sentence that packs purpose, return shape, and a usage example into two lines. It is front-loaded with the core function and has zero waste.

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 the tool's moderate complexity (3 params, 2 required, no output schema, no nested objects), the description is mostly complete: it explains the return structure and gives a use case. However, it does not explain what happens when no aircraft is found (the 'found' flag is mentioned but not what the caller should do with it), and it does not mention any required authentication or connection, but those are likely implied by the sibling `authenticate` tool. With good annotations and a clear return description, a 4 is justified.

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 input schema provides parameter names and types but no descriptions, and schema description coverage is 0%. The description mentions the radius in nautical miles ('raio em milhas náuticas') but does not clarify the units or format for lat/lon (assumed decimal degrees) or the default/optional nature of radius_nm. Since the description adds minimal parameter semantics beyond the schema's types, it barely compensates, so a baseline 3 is appropriate.

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?

A description states the tool's specific verb+resource: returns the closest aircraft to a point within a radius in nautical miles, and clarifies it returns { found, aircraft } with distance_nm and bearing_deg. It clearly distinguishes from siblings like flightradar_nearby (likely returns multiple nearby aircraft) and flightradar_aircraft by focusing on the single closest aircraft.

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 includes an example of a user query ('que avião é esse passando aqui em cima?') that signals a clear use case. However, it does not explicitly state when not to use this tool or name alternatives like flightradar_nearby, so it lacks exclusions but has clear context.

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