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

Goes well beyond the annotations (which only say it's non-readonly and open-world): it discloses that runs cost credits at a linked pricing page, that generation takes minutes, and that the call is asynchronous returning a run id. These are exactly the traits an agent needs to set expectations and avoid retry storms.

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?

Front-loaded with the primary action, then the photo-to-video variant, then cost and latency. Three tight sentences with no filler.

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?

No output schema exists, and the description compensates by explaining the return value (a run id) and the required next step (check_status). Cost, latency, defaults, and both input modes are all covered, so an agent has everything needed to invoke and follow up.

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%, so per-parameter meaning, enums, and duration constraints are already documented. The description restates the default model and resolution, which the schema's model field description already covers, so it adds little beyond the structured data.

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?

States a specific verb and resource ("Generate a video clip with sound from a text prompt") and explicitly covers the second mode ("animate a photo by passing image_url"). An agent can tell exactly what this produces without opening the schema.

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?

Gives concrete selection context: default model/resolution, the image_url switch for photo-to-video, and the follow-up step ("poll with check_status") that routes to a sibling. It stops short of stating when NOT to use this tool (e.g., vs. an image tool or the credits sibling), so it's clear context rather than full when/when-not coverage.

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