list_voices

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

No annotations provided, so description carries burden. It indicates a read-only operation ('List available'), but does not mention any limitations (e.g., pagination, rate limits) or authentication needs. For a simple listing tool, this is acceptable but not exemplary.

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, self-contained sentence with no filler. It efficiently communicates the tool's purpose.

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?

The tool has only two optional parameters and no output schema. The description covers the scope (stock and cloned voices) but does not mention what the response includes (e.g., voice IDs, names, preview URLs). For a listing tool, some output expectations would be helpful.

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?

Both parameters are already well-described in the input schema (filter_gender and filter_language). With 100% schema coverage, the description correctly does not repeat parameter details. However, it adds no additional context or examples 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 clearly states the tool's purpose: listing voices for avatar videos, specifying types (stock and cloned). It uses a specific verb 'list' and resource 'HeyGen voices', and distinguishes from sibling tools which are video creation/download.

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 usage when you need to browse available voices, but provides no guidance on when not to use it or alternatives. Sibling tools are all video generation, so there's no direct alternative for listing voices, but the description could mention that this is the only voice listing tool.

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