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

The annotations only declare readOnlyHint=false; the description goes far beyond that by describing the placeholder scene creation with prompt 'Gap', split behavior for scenes/voice clips at at_ms, stretch behavior for text/stills/captions/stickers, and a comprehensive list of refusal conditions. It also names each refusal and the fix, which is exactly the behavioral context an agent needs for a mutation tool.

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?

Front-loaded with the core action and its ripple effect, then adds placeholder, split/stretch, and refusal details in order of importance. The final refusal clause is a dense run-on, but every sentence carries operational value for a destructive timeline edit.

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?

No output schema exists, so the description must carry the full behavioral burden — and it does, covering side effects, placeholder creation, split/stretch semantics, and failure modes. An agent can call this tool correctly without needing any additional documentation.

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 100%, so the baseline is 3, but the description adds real meaning: at_ms is where time opens, length_ms corresponds to one placeholder scene, and the interaction of at_ms with scene edges (100ms refusal) is clarified. It doesn't fully restate every schema constraint, so not a 5.

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 precise verb and resource — open empty time at a millisecond offset on every lane — and immediately explains the ripple effect on subsequent content. It is clearly distinguishable from siblings like studio.ripple_delete, studio.shift_clips, or studio.cut_range because it describes insertion, not removal or shifting of existing clips.

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?

Explains the intended outcome and the follow-up action (fill the placeholder with update_scene/generate_scene or footage). It does not explicitly name alternatives such as shift_clips or ripple_delete or state when those should be preferred, so it stops short of full routing guidance.

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