Validate keyframe or expression animations in After Effects by specifying composition and layer indices to confirm expected behavior.
Test animation functionality in After Effects
| Name | Required | Description | Default |
|---|---|---|---|
| compIndex | Yes | Composition index (usually 1) | |
| operation | Yes | The animation operation to test | |
| layerIndex | Yes | Layer index (usually 1) |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description must disclose behavioral traits. It only says 'test', which is ambiguous—does it apply changes or remain read-only? It does not mention side effects, return values, or any safety profile, leaving the agent without critical information.
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?
The entire description is one short sentence, which is appropriately concise in length, but it merely restates the tool name. This is under-specification rather than effective conciseness because it uses the sole sentence without providing any substantive information.
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 tool with no annotations, no output schema, and three required parameters, the description is wholly inadequate. It fails to explain what 'testing' means, how operation/comp/layer parameters interact, what the agent should expect as a result, or when this tool should be chosen over the many sibling animation tools.
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?
The schema provides 100% description coverage for the three parameters, including the operation enum and brief guidance ('usually 1'). The description adds no parameter-level insight beyond the schema, so the baseline of 3 applies.
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 "Test animation functionality in After Effects" is a near-tautology of the tool name 'test-animation'. It identifies the domain (After Effects animation) but does not specify what testing entails, nor does it distinguish this tool from siblings like setLayerKeyframe or setLayerExpression.
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?
The description provides no guidance on when to use this tool versus alternatives. With many sibling tools for setting keyframes and expressions, there is no explanation of whether this tool is for validation, comparison, or actual mutation, nor any exclusions or prerequisites.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.