Create a video (from scenes)

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

With no annotations, the description carries full burden. It discloses asynchronous rendering (returns videoId immediately), default draft render (watermarked, free), and that final render consumes quota. Could mention error handling or rate limits, but covers key behavioral traits.

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 well-structured sentences with no wasted words. Front-loaded with the main purpose and key behavioral details.

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 tool with 10 parameters and nested objects, the description provides a high-level overview covering async, quota, and sibling alternative. It could include expected output or common errors, but is reasonably complete given the schema richness.

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 90% (high), so baseline is 3. The description adds valuable context beyond the schema: async behavior, draft/final distinction, and alternative tool advice. It doesn't repeat param details but provides complementary guidance.

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 'Create a Synthesia avatar video from one or more scenes' with specific verb and resource. It distinguishes from the sibling tool create_video_from_template by noting when to prefer that alternative for visually rich layouts.

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?

Explicit guidance on when to use this tool vs create_video_from_template, and clear instructions on render_mode: default to draft for iteration, use final only on explicit user approval. Also mentions asynchronous workflow and to check progress with get_video.

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