Set or clear an expression on an After Effects effect parameter using layer, effect, property, and expression values; omit compositionName to use the active comp.
After Effects: set (or clear with "") an expression on an effect parameter.
| Name | Required | Description | Default |
|---|---|---|---|
| layer | Yes | Layer name or 1-based index. | |
| effect | Yes | ||
| property | Yes | ||
| expression | Yes | ||
| 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 this is a write operation (readOnlyHint=false) that is not destructive and not open-world, so the safety profile is carried by structured data. The description adds the non-obvious fact that an empty string clears the expression, but says nothing about overwriting an existing expression or what happens if layer/effect is not found.
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 no filler; the clearing behavior is stated inline rather than buried. Nothing here is wasted.
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 5-parameter mutation tool with 40% schema coverage and no output schema, the description is thin: it does not explain how to identify the effect or property (name vs index), nor confirm that the existing expression is replaced. Annotations cover the safety profile, but the identifier semantics an agent needs to call it correctly are absent.
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 only 40%: 'layer' and 'compositionName' are documented in the schema, but 'effect' and 'property' have no description in either the schema or the description. The description mentions 'effect parameter' only incidentally and never explains that effect/property accept names or 1-based indices, nor what expression syntax is expected.
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 verb (set/clear) and a specific target (an expression on an effect parameter), which narrows it meaningfully versus a generic property expression tool. It does not, however, name or distinguish itself from the closely related siblings ae_setExpression and ae_applyExpressionTemplate.
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 parenthetical '(or clear with "")' gives one concrete usage case for removal, which is genuinely useful. There is no guidance on when to prefer this over ae_setExpression, ae_applyExpressionTemplate, or ae_setEffectProperties, so routing is left to inference.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.