list_voices

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

With no annotations, the description carries the burden of behavioral disclosure. It indicates that the returned objects include compatibility flags (emotion_support, support_locale) that affect downstream create_video calls, providing useful coupling context. Although it does not mention pagination or rate limits, the list operation is clearly read-only and the main behavioral nuances are surfaced.

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 purpose, then a targeted usage hint and compatibility explanation. Every sentence earns its place; no redundancies.

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 simple list tool with no output schema, the description covers the main purpose, key return fields, filtering intent, and downstream compatibility. It lacks explicit pagination/limit behavior, but that is covered in the schema and the overall description is adequate for an agent to invoke it 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% with each parameter already described. The description adds semantic guidance—'Filter by language and gender to find a voice'—but does not materially increase understanding of the parameter formats or constraints, so the baseline 3 applies.

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 the specific verb 'List' with the resource 'HeyGen voices' and enumerates the returned fields (voice_id, language, gender, preview_audio URL), clearly distinguishing it from sibling tools like list_avatars. It also explicitly connects the purpose to selecting a voice for create_video, further clarifying scope.

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 states when to use this tool ('to find a voice for create_video') and provides the key filtering dimensions (language and gender). It gives clear context without naming alternative tools explicitly, which aligns with 'clear context, no exclusions'.

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