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

With no annotations, the description carries the behavioral burden. It communicates that this is a read-only, no-cost discovery operation ('Free discovery tool') and that the result reflects the current state ('currently supported'). For a zero-parameter list tool, this is sufficient behavioral disclosure.

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 short sentences, front-loaded with the most important signal ('Free discovery tool'), followed by the resource and usage instruction. Every sentence earns its place and there is no 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?

For a zero-parameter listing tool, the description adequately tells the agent what it returns, when to use it, and that it is free. No output schema exists, but the return value is self-explanatory from the tool name and description.

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 tool has zero parameters, so there is no per-parameter meaning for the description to add. The baseline of 4 applies, and no compensation is needed.

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 states a specific action ('List') and a precise resource ('licensing authorities currently supported by the deterministic taxi/PHV rule bundle'). The 'Free discovery tool' framing and the unique resource distinguish it from sibling tools like compare_licensing_requirements and taxi_licence_preflight.

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 gives explicit placement guidance: 'Use before requesting a paid decision.' This tells an agent when to call it, though it does not explicitly name alternative tools or describe when not to use it.

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