extend_video

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

With no annotations, the description carries full burden. It discloses the async operation and the need for a matching model. It does not detail side effects or error states, but the workflow is transparently described.

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 concise sentences immediately convey the tool's purpose, prerequisite, and async workflow without any redundant or extraneous information.

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 description covers the core workflow (async, poll, download) and important constraints (model compatibility). Since an output schema exists, the omission of return value details is acceptable. Minor gaps in error handling or status polling frequency are not critical.

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%, but the description adds valuable semantics: that the model must match the original and that Lite does not support extension. This goes beyond the schema's basic descriptions.

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 precisely states it extends a previously generated video using a continuation prompt and requires an operation ID. It clearly distinguishes from siblings like generate_video or animate_image by specifying the prerequisite operation ID.

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?

It explicitly mentions the requirement of the operation ID and the async nature, directing to video_status and download_video for polling and retrieval. It does not explicitly exclude other use cases or provide when-not-to-use scenarios, but the context is clear enough.

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