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

Annotations already mark it as non-read-only, open-world, and non-destructive, and the description adds important behavior beyond them: it starts a background job, costs credits, and returns a project id intended for wait_for_video_project. It also discloses authorization and content-safety constraints. There is no contradiction with the annotations.

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 compact and front-loads the most important constraint, then states the purpose, input requirements, and async cost/return behavior. Every sentence carries useful information 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?

Given the rich input schema, full parameter description coverage, and an output schema, the description is complete enough for an agent to select and invoke the tool correctly. It covers the key functional scope, safety constraints, required asset types, cost/background-job behavior, and next step for retrieving results.

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 description coverage is 100%, so the schema already explains parameters such as assets, resolution, start_seconds, end_seconds, style, and generation_mode. The description reinforces that a portrait photo and audio file are required and that text alone is not accepted, but it does not add much detail about the nested style, resolution, or timing parameters beyond what the schema provides.

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 action and resource: it animates a still portrait so it speaks an existing audio recording. It also distinguishes the tool from text-only generation and speech synthesis by explicitly saying text alone is not accepted and it does not synthesize speech.

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?

Provides clear usage context and exclusions: use only with the user's own likeness or authorized content, and do not use for impersonation, deception, sexual content, or minors. It also clarifies that a portrait photo and audio file are required, though it does not explicitly route the agent to a named sibling alternative for lip-sync or audio-to-video cases.

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