Create a rectangle on a master spread
AI agents use create_master_rectangle to create or update resources in InDesign UXP MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your InDesign UXP MCP Server environment.
This tool creates new design content (a rectangle shape) on a master spread, which is a reversible modification. Master spreads in InDesign are template pages that propagate changes to document pages; adding a rectangle here affects document layout globally but is not destructive (the rectangle can be deleted or modified).
From the tool's definition Tool name: 'create_master_rectangle'; description: 'Create a rectangle on a master spread'. The verb 'create' indicates the tool adds a new graphical object (a rectangle shape) to a master spread in an InDesign document.
Documented attack patterns abuse exactly the kind of access create_master_rectangle gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and InDesign UXP MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for create_master_rectangle:
{
"version": "1",
"default": "deny",
"tools": {
"create_master_rectangle": {
"limits": [
{
"counter": "create_master_rectangle_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}create_master_rectangle 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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Create a rectangle on a master spread. It is categorised as a Write tool in the InDesign UXP MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the InDesign UXP MCP Server MCP server in PolicyLayer and add a rule for create_master_rectangle: 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 UXP MCP Server. Nothing to install.
create_master_rectangle 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 create_master_rectangle 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 create_master_rectangle. 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.
create_master_rectangle is provided by the InDesign UXP MCP Server MCP server (theloniuser/indesign-uxp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 135 InDesign UXP MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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135 InDesign UXP MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.