extract_frame

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

With no annotations, the description discloses some behavior: default is the last frame, upload=true hosts a temporary public URL, and output is PNG. However, it doesn't mention side effects like asset creation or how to access the saved frame, leaving some behavioral aspects unclear.

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 core purpose, followed by a practical use case and upload behavior. No redundant wording; every sentence earns its place.

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 three-parameter tool with no annotations, the description covers the core function, default behavior, upload option, and a common workflow. It omits specifics about time_s and output details, but an output schema exists, so return values may be documented there.

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 0%, so the description must compensate. It clarifies 'video' (local path or URL) and 'upload' (hosts on temporary public URL). 'time_s' is only implied by 'default = LAST frame,' without stating that it selects a specific frame or its units, leaving ambiguity.

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 the tool's function clearly: 'Save one frame of a video (local path or URL) as PNG; default = LAST frame.' It uses a specific verb and resource, and the mention of bridging continuity with generate_seedance_first_last distinguishes it from siblings.

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 concrete usage guidance: 'Use the last frame of clip N as image_first of clip N+1...' and explains when upload=true is useful. It doesn't explicitly state when not to use it or name alternatives, but the reference to a sibling tool indicates integration context.

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