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

Annotations only declare the non-read-only, non-destructive, closed-world profile. The description adds the key side effect that the annotations cannot convey: the clip is split at `time` and the remainder of that track is pushed later, so the timeline length changes. It omits error/edge behavior (e.g. time outside any clip, no clip under the playhead) and whether an identifier for the new still is returned.

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 sentence that front-loads the core action and then explains the mechanical consequence. No filler, no redundant restatement of the title.

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 4-parameter mutation with no output schema and partial schema coverage, the description supplies the essential mechanics and the ripple side effect. Gaps are minor: nothing about failure modes when `time` does not land inside a clip, and no hint about the return value.

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 50%: `clipId` and `projectId` defaults are already documented in the schema. The description does add the `duration` default of 1, which the schema lacks, and ties `time` to the split position — genuine but modest value beyond the structured fields, so this sits at the baseline rather than above it.

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 action (hold the frame at `time` for `duration`) and, crucially, the mechanical result: the clip is split and a still is inserted. An agent immediately knows this produces a freeze-frame, not a plain split or an added clip. It does not name or contrast with siblings such as split_clip, punch_in, or add_clip, which keeps it short of a 5.

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?

Usage is only implied by the effect semantics — an agent can infer this is the tool for freezing a moment. There is no explicit when-to-use, when-not-to-use, or alternative routing against split_clip or add_clip, which matters given the very large sibling set.

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