extend_video

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

With no annotations, the description must carry behavioral disclosure. It explains the core action and duration range but omits details like authentication, rate limits, side effects (e.g., file uploads for video_path), and failure modes. The model compatibility caveat is only in the schema, not the description.

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 two sentences, front-loaded with the purpose, and contains no filler. It is appropriately sized for the tool's complexity.

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 the basic workflow but does not mention the three mutually exclusive source options (video_url, video_path, video_file_id) or the output_path. It also omits that model grok-imagine-video-1.5 does not support extension. While the schema fills many gaps, the description alone would leave users uncertain about the full input flexibility.

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 coverage is 100%, so the description needs to add limited extra meaning. It mentions source URL and prompt, but the schema already describes each parameter fully. The 'default 6' is also already in the schema, so the description adds no novel semantics.

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 a specific verb ('Extend') and resource ('an existing video'), clearly distinguishing it from siblings like generate_video and edit_video. It also names the underlying API, adding specificity.

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 provides clear context: use for extending an existing video with a prompt. It does not explicitly contrast with generate_video or edit_video, but the context is unambiguous. No exclusions are stated, so not a 5.

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