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

With no annotations provided, the description carries the burden of behavioral disclosure. It adds 'Free', which is a useful access/cost trait, and 'you can pass to submit_video_job', which clarifies the returned values are directly usable. It does not detail output format or pagination, but for a simple zero-parameter list operation these gaps are minor.

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 two short sentences with no filler. The primary purpose is front-loaded, and the secondary detail about cost is brief and relevant. Every word earns its place.

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 no-parameter listing tool with no output schema, the description provides enough context: it returns narration voices that can be passed to submit_video_job. It could explicitly state the return format, but that is a minor omission given the straightforward nature of the operation.

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 the baseline is 4. There is no parameter documentation needed, and the description adds no unnecessary parameter-specific details.

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 'List' with a clear resource 'narration voices' and ties it to 'submit_video_job', which distinguishes it from the sibling job-related tools. It explicitly tells the agent what the tool does and how the output will be used.

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 clearly implies when to use this tool: before submit_video_job, to obtain valid voice options. It doesn't explicitly list exclusions or alternatives, but the tool's focused purpose and sibling set make those unnecessary. The mention of 'Free' also helps the agent understand there is no cost barrier.

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