Set the active layer
AI agents use set_active_layer to create or update resources in Indesign — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Indesign environment.
This tool changes InDesign document state (which layer is active) without creating, reading, or deleting content. It's reversible (you can set a different layer active), so it's not Destructive. It doesn't execute arbitrary code or trigger external operations beyond InDesign's own UI state management, so it's not Execute.
From the tool's definition Tool modifies document state by setting the active layer, which changes internal document properties but is reversible—switching to a different layer undoes the effect.
Documented attack patterns abuse exactly the kind of access set_active_layer gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Indesign, and nothing reaches the server without passing your rules. This is the rule we recommend for set_active_layer:
{
"version": "1",
"default": "deny",
"tools": {
"set_active_layer": {
"limits": [
{
"counter": "set_active_layer_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_active_layer stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Set the active layer. It is categorised as a Write tool in the Indesign MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Indesign MCP server in PolicyLayer and add a rule for set_active_layer: 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 Indesign. Nothing to install.
set_active_layer is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the set_active_layer 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 set_active_layer. 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.
set_active_layer is provided by the Indesign MCP server (lucdesign/indesign-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Indesign, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
36 Indesign tools catalogued and risk-classified — across an index of 43,000+ MCP servers.