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

Annotations only cover the safety profile (readOnly=false, destructive=false, openWorld=true), so the async contract is genuine added value: the tool returns a job with an id and status, and completion requires polling get_video. The billing caveat (duration drives cost, minimum-length charges possible) is a non-obvious operational trait worth disclosing.

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?

Three short sentences with the core action first, then cost, then async contract. No filler, though the cost sentence is slightly dense with two distinct ideas (duration driver plus minimum billing).

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 no output schema, the description usefully characterizes the return value ('a job with an id and status') and names the follow-up tool, which is the key gap an agent would otherwise hit. The 6-parameter, nested-params surface is well covered by the schema itself.

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 documents tier, model, params, provider and title_id in detail, including the tier-cancellation warning. The description only adds the connection that duration (a params key) is the cost driver; that is marginal above the baseline of 3.

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 states a specific verb and resource ('Generate a video clip') and implicitly disambiguates from generate_image, generate_audio and generate_text by naming the media type. It does not explicitly contrast with the closest sibling remix_video, so it falls short of full sibling differentiation.

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 gives real usage context: estimate cost first, and poll get_video for the result after the async call. However it never names estimate_media_cost (the actual sibling) nor states when to prefer a different generation tool or when not to use this one, leaving routing partly to inference.

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