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

The annotations already declare this a safe, idempotent, non-open-world read, so the description only needs to add content-level context. It does that by telling the agent the result includes per-resolution per-second pricing and maximum clip duration, which is material for answering cost and feasibility questions. It doesn't say whether the catalog is static or live, but that is a minor gap given the annotation coverage.

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 short sentences, with the payload description first and the call trigger second. Every clause carries information and nothing is repeated from the annotations or the schema.

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?

There is no output schema, so the description has to characterize the return value, and it identifies the three fields an agent needs: available models, per-resolution per-second cost, and max clip length. That is sufficient for a zero-parameter catalog lookup; only the static-vs-live nature of the data is left unstated.

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?

The tool takes zero parameters, which is the baseline-4 case. The description correctly makes no parameter claims and spends its space on what the call returns.

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 names the resource (video models) and the three attributes returned: price per second at each resolution and maximum clip length. That is a concrete, verifiable purpose. It doesn't explicitly distinguish itself from a close sibling such as list_image_models or estimate_video_cost, so it stops short of a 5.

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?

"Call it when the user asks whether you can make video" gives a clear trigger condition rather than leaving usage implied. It doesn't mention when to prefer estimate_video_cost or generate_video instead, so the guidance is clear but lacks alternatives.

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