video_composite_layers

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

With no annotations, the description carries full burden. It explains supported operations (alpha compositing, opacity, positioning, transforms, timing, masks), deferred features, and the deterministic layer-plan receipt. It also mentions dry_run for validation. It does not cover auth or rate limits, but the behavioral scope is well described without contradictions.

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 well-structured with a clear first paragraph for main purpose, a second for deferred features, and a third for parameters. Every sentence adds value, no fluff, and it's appropriately front-loaded.

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?

Given the tool's complexity and presence of an output schema, the description covers inputs, features, and limitations well. It mentions the layer-plan receipt but could briefly describe the output (composited media file). Overall, it is reasonably complete for agent decision-making.

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 description must compensate. The Args section explains each parameter: spec_path (required JSON spec), output_path (optional destination), save_layer_plan (optional receipt path), dry_run (validate without render). This adds crucial meaning beyond the schema's simple types and titles.

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 it composites ordered image/video layers from a JSON spec, listing supported features and deferred features. This provides a specific verb+resource and distinguishes it from simpler siblings like video_overlay by its JSON-spec input and advanced compositing capabilities.

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 implies when to use (for complex layer compositing with a JSON spec) and explicitly states deferred features (non-normal blend modes, rotation) as limitations, guiding agents away from using it for those. However, it does not explicitly name alternative tools for those cases, leaving room for improvement.

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