Time-stretch an After Effects layer by percentage or set its playback speed to create slow motion, fast motion, or reverse playback in the active or named composition.
After Effects: time-stretch a layer (stretch % — 200 = half speed, -100 = reverse) or set playback speed %.
| Name | Required | Description | Default |
|---|---|---|---|
| layer | Yes | Layer name or 1-based index. | |
| speed | No | ||
| stretch | No | ||
| compositionName | No | Comp name; omit to use the active comp. |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare the operation is mutating but non-destructive and closed-world, so the safety bar is lower. The description adds real value by disclosing the meaning of negative values (-100 = reverse) and the 200 = half-speed convention. It does not say whether existing keyframes/in-out points shift, whether speed and stretch are mutually exclusive, or what a call 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?
A single front-loaded sentence with a compact parenthetical that carries the most useful semantic detail. Nothing is redundant, though the parenthetical ends up doing double duty for a parameter the schema leaves blank.
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?
Hmm—let me be precise: with no output schema, a mutation flag set, and two of four parameters undocumented, the description should clarify speed-vs-stretch exclusivity and the effect on keyframes. It covers the numeric conventions well but leaves those interaction questions open, so it is adequate rather than complete.
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%: 'layer' (name or 1-based index) and 'compositionName' are documented in the schema. The description rescues 'stretch' with a concrete numeric convention but leaves 'speed' undefined numerically (100 = normal?) and never explains whether stretch and speed are alternatives or how they interact when both are supplied.
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?
Names a specific verb (time-stretch) and resource (a layer) with the After Effects namespace prefix, and the two operating modes (stretch % vs playback speed %) are stated. An agent can distinguish it from ae_timeRemap or ae_trimLayer by the vocabulary, though the description never explicitly contrasts them.
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: the description presents 'stretch' and 'or set playback speed %' as two paths but never says which to pick, nor when this tool is preferable to ae_timeRemap, ae_trimLayer, or keyframe-based speed changes. No preconditions (e.g., layer must be selected, comp must be open) are stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.