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

Beyond the readOnly/idempotent annotations, the description adds that nothing is saved or changed, that rendering happens in the user's tab, that output is a single labelled contact sheet, and that props apply only to this render. It also explains the meaning of per-frame content share, which helps the agent interpret anomalous frames.

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 front-loaded with the core action and then moves efficiently through frame selection, resolution, prop merging, and result interpretation. Each sentence contributes operational detail without repetition.

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?

With annotations covering safety and idempotency, and no output schema, the description provides enough about the returned contact sheet, labelling, resolution, and content-share signal for an agent to invoke and interpret the tool correctly.

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 high at 75%, and the description adds useful semantics beyond the schema for the two most nuanced parameters: atFrames has a 12-frame cap and a meaningful default spread with scene-boundary labels, while props are merged over composition props for this render only. The token and id parameters are left to the schema, which is acceptable given their coverage.

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 a specific verb and resource: it renders frames of a composition in the user's tab and returns a labelled contact sheet. It explicitly scopes the operation as non-persistent, which distinguishes it from mutation-oriented siblings like update_composition or create_composition.

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 clear invocation context by explaining that omitted atFrames produces an even spread plus scene joins, and that higher-resolution single frames are for checking detail. However, it does not explicitly name alternatives such as check_playback or get_composition, so the agent must infer when this visual inspection tool is preferable.

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