List voices

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

With no annotations provided, the description carries the full burden and does exceptionally well: it reveals the exact resolution order (env var, file, first file, fallback model default), which behaviorally affects what the tool returns. This is precisely the kind of contextual detail an agent needs beyond the schema.

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, the first clearly scopes the listing and the second enumerates the resolution order. Every phrase adds value and the default-voice resolution rule is stated in a compact, order-relevant manner.

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 output schema exists, the description does not need to explain return format. It fully explains what this tool does (list voices and default voice) and even how the default is determined, which is the behavioral nuance essential for an agent to pick the right voice via speak.

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 takes zero parameters, so the schema is already complete (100% coverage) and there is nothing for the description to elaborate on. Baseline 4 applies since there is simply no parameter information 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?

States a specific verb ('List') and resource ('Kokoro voices available to the speak tool') and also includes the currently selected default voice. The mention of 'speak tool' clearly distinguishes it from the sibling speak tool, making its function unambiguous.

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 implies this tool should be used to discover available voice options before using the speak tool, especially because it names the speak tool as the consumer. It clearly states the resolution order for the default voice, giving immediate context, but it does not explicitly say when not to use it or mention alternative tools.

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