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

Annotations already declare this is a non-read-only but non-destructive mutation, and the description adds a genuinely useful constraint not in the annotations: only unlocked tracks are affected. It says nothing about whether the split is undoable, what happens to effects/keyframes/transitions at the split point, or what the tool returns.

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?

Two short sentences, zero filler, with the scoping rule front-loaded ahead of the conditional fallback. Nothing could be removed without losing meaning.

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?

For a four-parameter mutation with no output schema, the description covers the essential behavior: what gets split, when, and on which tracks. The remaining gap is trackIds semantics and post-split effects, but the core call decision is well supported.

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 only 25% (only projectId is documented), so the description must compensate. It does explain clipId and time semantics well, but trackIds is left unexplained — the 'unlocked tracks' clause hints at track scoping without stating that trackIds restricts the operation to those tracks.

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 gives a specific verb and resource ('Split at a timeline time') and immediately defines the two scoping modes (single clip via clipId vs. all clips under the time). That distinguishes it from sibling mutations like trim_clip or slip_clip, though it never names those alternatives explicitly.

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 clearly states the branch condition between the clipId and no-clipId modes, which is real usage guidance. It does not say when to prefer split_clip over adjacent tools (trim_clip, slip_clip, delete_ranges), so an agent still has to infer the boundary from sibling names.

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