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

No annotations are provided, so the description carries the full burden for a mutation tool. It does not disclose that this writes to the project timeline, what expectedVersion concurrency enforcement means on conflict, or what state the placeholder enters after insertion; only the forward-looking 'ready for a generation prompt' adds any lifecycle context.

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?

A single compact sentence with the action and target front-loaded and no filler. The trailing section references (§7.5, §11.5) add no operational meaning for an agent and could be dropped.

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 a write operation, no annotations, no output schema and zero parameter documentation, the definition is far too thin. An agent cannot tell what version-conflict behavior to expect, what the created clip looks like on return, or how the placeholder relates to the generation tools that will fill it.

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 0% across 8 parameters (7 required), so the description must compensate and does not. It touches only track and kind implicitly, leaving expectedVersion (an obvious optimistic-concurrency token), startMs/durationMs, sceneId and projectId entirely undefined in prose.

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?

States a specific verb and resource ('Add a video/audio placeholder clip to a track') and adds the intent ('ready for a generation prompt'). It does not explicitly name how it differs from siblings like asset.replace_placeholder or shot.generate_video, and the 'video/audio' phrasing understates the kind enum, which also includes image, music, sound_effect, ambience and voice.

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 when-to-use or when-not-to-use guidance, and no routing to alternatives such as timeline.batch for bulk inserts or asset.replace_placeholder for later replacement. The phrase 'ready for a generation prompt' hints at a workflow stage but leaves the selection decision to inference.

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