Loop video

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It adds a key trait: 'Fast — no re-encoding,' which highlights performance and output quality. However, it omits other behavioral details such as how conflicting parameters (plays vs. target_duration) are resolved, whether existing output files are overwritten, or any format compatibility constraints. This is sufficient for a simple tools but leaves some gaps.

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 exceptionally concise: two sentences that front-load the core purpose and then add a valuable performance trait. Every word earns its place, with no redundancy or filler. It is well-structured for quick scanning.

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 four parameters and no output schema, the description covers the essential behavioral aspects: the two looping modes and the 'no re-encoding' characteristic. It is mostly complete, though it does not specify behavior when neither 'plays' nor 'target_duration' is provided, or what the default output path is. These are minor gaps given the schema fills in parameter details.

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% description coverage for all four parameters, so the baseline is 3. The description reinforces the two modes ('a number of times' vs 'fill a target duration') but does not add detailed semantics beyond what the schema provides. It correctly aligns with the schema's parameter descriptions, giving no additional value.

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 function: 'Repeat a video back-to-back a number of times, or long enough to fill a target duration.' It specifies the action (repeat), the resource (video), and the two modes (count-based or duration-based). This distinguishes it from all sibling tools, which perform other video operations.

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 clear usage context by explaining the two modes of operation: repeating a specific number of times or filling a target duration. While it doesn't explicitly state when not to use this tool or name alternatives, none of the sibling tools serve the same looping purpose, so the guidance is adequate. It implies that this is the go-to tool for video looping.

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