This record as markdown: /tools/ae/ae-add-expression.md
What ae_add_expression does on Ae
AI agents invoke ae_add_expression to trigger actions in Ae. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call: builds kicked off, notifications sent, workflows started.
Why ae_add_expression is rated High
This tool executes arbitrary JavaScript code within After Effects. An AI agent could inject malicious or unintended JavaScript expressions that run in the AE scripting environment, potentially causing unintended side effects, crashing the application, or executing host-level operations via AE's scripting API. The 'code-driven' nature confirms arbitrary code execution, making this Execute category with high severity.
From the tool's definition Add JavaScript expressions to properties for dynamic, code-driven animations
Attacks that exploit this kind of access
The rule that runs ae_add_expression safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Ae, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For ae_add_expression, this is the rule to start with:
ae_add_expression stays usable, but rate-capped: a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Ae, apply this rule, and every ae_add_expression call is checked against it from then on.
Questions about ae_add_expression
Add JavaScript expressions to properties for dynamic, code-driven animations. It is categorised as a Execute tool in the Ae MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Ae MCP server in PolicyLayer and add a rule for ae_add_expression: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Ae. Nothing to install.
ae_add_expression is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the ae_add_expression rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for ae_add_expression. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
ae_add_expression is provided by the Ae MCP server (ae-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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