extend_video

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

No annotations are present, so the description carries the behavioral disclosure burden. It discloses key traits: the extension starts from the last second, input requirements, fixed output format/resolution, and cost. It does not cover all behaviors (e.g., async behavior, error handling), but the provided details add substantial transparency beyond the schema.

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 well-structured and concise: a lead sentence with the core purpose, followed by bulleted requirements and cost. Every sentence adds value, no filler or redundancy. It is front-loaded and easy to scan.

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?

For a tool with no output schema and no annotations, the description covers the essential context: input constraints, output format, cost, and continuation behavior. It does not explain the wait parameter's implications (async workflow) or how to retrieve the result, but the schema documents wait and the sibling get_video_status implies the flow. Overall, it is fairly complete.

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 input schema already has 100% coverage with descriptive comments for all parameters, so the baseline is 3. The description adds context about input video constraints (duration/fps/resolution) and output resolution, which relates to the video parameter, but it does not provide per-parameter semantics beyond the schema. This is adequate but not exemplary.

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 uses the specific verb 'extend' with the resource 'existing video' and a precise duration (7 seconds). It clearly distinguishes from sibling tools: generate_video creates new videos, interpolate_frames alters frame rates, and get_video_status checks status. No ambiguity about what this tool does.

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?

The description establishes clear context: use this tool when you have an existing video and need to extend it. It also provides input constraints (duration, fps, resolution) that help the agent decide if the tool is appropriate. However, it does not explicitly name alternatives or state when not to use it, so it falls short of a 5.

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