extend_video

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

With no annotations provided, the description carries the full burden. It adds constraints: video_url must be .mp4 (2-15 s), duration 2-10 seconds, and a default model. However, it does not disclose side effects, authorization needs, rate limits, or output behavior. The description provides moderate 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 concise at 7 lines, with a clear opening sentence followed by structured Args bullet points. Every sentence adds value without redundancy.

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?

The description covers all parameters with constraints and defaults, and an output schema exists to explain return values. Still, it could mention typical errors or prerequisites (e.g., video must be generated by this system). Overall, it is complete given the schema and parameter count.

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 description adds rich meaning beyond the input schema, which has 0% description coverage. It explains 'prompt' as 'what should happen in the extended segment,' 'video_url' as 'Public URL... (.mp4, 2–15 s),' 'model' with default, and 'duration' with range (2–10, default 6). This fully compensates for the schema's lack of descriptions.

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 clearly states the tool's action: 'Extend an existing video with a follow-up prompt.' It uses a specific verb ('Extend') and resource ('existing video'), distinguishing it from sibling tools like generate_video which likely creates new videos from scratch.

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?

No guidance is provided on when to use this tool versus alternatives. The description lists parameters but does not specify context, prerequisites, or situations where another tool (e.g., generate_video) would be more appropriate.

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