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

Annotations already declare this as a safe, read-only, non-destructive operation, so the bar for behavioral disclosure is lower. The description adds that frames are composited 'as the player shows them' and returned as images, but it does not explain output limits, image handling, or how multiple frames are returned.

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 a single tightly worded sentence with no wasted language. It front-loads the core output concept and stays appropriately brief.

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 has 10 parameters and no output schema, so the description should carry some burden in explaining what comes back. It says images are returned, but it does not clarify multi-frame behavior, contact sheets, or inline versus referenced image output, leaving some contextual gaps.

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 description coverage is 80%, so most parameters are already documented in the schema. The description adds no parameter-specific meaning beyond the schema, which is acceptable given the high coverage but not a value-add.

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 resource and output: composited timeline frames as seen by the player, returned as images. It is specific enough to understand what the tool produces, but it does not explicitly differentiate itself from siblings such as grab_frame, filmstrip, or show_preview.

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?

There is no guidance on when to use this tool versus alternatives like grab_frame, filmstrip, or show_preview. The intended usage is only implied by the tool name and description.

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