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

Beyond the annotations (readOnly, idempotent, non-destructive), the description discloses that begin/end parameters are ignored, that historical data is unavailable, and that no API key is needed. It also describes the return fields, providing substantial behavioral context without contradicting annotations.

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?

Two sentences, front-loaded with the core action and data returned, then limitations and alternative. Every sentence serves a purpose with 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?

For a single-record lookup with strong annotations and full schema coverage, the description covers purpose, usage boundaries, parameter quirks, and return fields. Though there is no output schema, the listed return fields compensate. The description is complete enough for an agent to choose and invoke correctly.

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 baseline is 3. The description reinforces the ICAO24 format and explains ignore behavior of begin/end, but the schema already provides this information. No additional parameter meaning is added 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?

The description uses a specific verb ('look up') and resource ('one aircraft by its ICAO24 transponder address'), and explicitly lists the returned fields (position, altitude, speed, heading, etc.). This clearly distinguishes it from siblings like get_flights or get_states, which handle multiple aircraft or flight lists.

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 states when to use the tool (for current position) and when not to (historical flight legs are not available). It explicitly points to an alternative (get_flight_route in the flights pack) and notes that no authentication is needed ('Keyless'), giving clear context for selection.

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