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

With no annotations, the description carries the burden of behavioral disclosure. It mentions that processing happens in the browser, that it consumes more credits per run than other workspaces, and that Day Pass does not include the workspace. However, it omits input requirements, side effects, and output delivery details.

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 core purpose is stated in one clear, front-loaded sentence. The remaining sentences provide credit and pricing details that are relevant but add length; they are still useful and not excessive. Overall, it is efficient with only minor potential for trimming.

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 tool is low-complexity with no parameters and no output schema, so the description sufficiently conveys the action and output format. It also provides workspace and credit context. It does not specify how the input video is selected or how the resulting thumbnail is returned, but these gaps are acceptable given the minimal interface.

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 has zero parameters, so there is nothing for the description to explain. The baseline for zero parameters is 4, and the description does not need to compensate for any schema coverage gaps.

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 opens with 'Extract Video Thumbnail — Extract a frame from video as a JPEG thumbnail image,' which clearly identifies the specific verb, resource, and output format. This distinguishes it from the many other video tools in the sibling list by focusing on thumbnail extraction.

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 provides useful context about credit usage and workspace restrictions but does not explicitly state when to use this tool versus alternatives or name any sibling tools. The credit/day-pass information implies conditions for use but lacks direct comparison guidance.

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