create_avatar_video

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

No annotations are provided, so the description must disclose behavioral traits. It does not mention whether the operation is synchronous or asynchronous, what the response contains, credit consumption, or any side effects. The schema includes a test_mode parameter, but the description ignores it, missing an important behavioral cue.

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 very short with two sentences, making it efficient. However, it lacks structure (e.g., bullet points or clear sections) that could improve readability. It is concise but not optimally organized.

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?

With 6 parameters and no output schema or annotations, the description should provide more context. It does not explain return values, async behavior, credit usage, or prerequisites (e.g., needing avatar_id from list_avatars). The tool is moderately complex, and the description leaves significant gaps.

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 input schema has 100% description coverage, so the baseline is 3. The description adds no additional meaning beyond the schema; it does not explain any parameters or their relationships. It relies entirely on the schema, which is acceptable but not improved.

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 creates a HeyGen avatar video with specific avatar and voice selection. It explicitly mentions 'precise control over avatar,' which hints at its specific use case. However, it does not fully distinguish from siblings like generate_creative_video or generate_video, which may also involve avatars.

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 says 'Use for precise control over avatar,' which implies when to use this tool, but it does not provide exclusions or explicitly name alternatives. There is no guidance on when not to use it or what differentiates it from other generation tools.

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