system_set_variable

THE RISK

Medium Risk

Why system_set_variable needs a policy

This tool modifies AutoCAD's internal state and configuration rather than drawing data directly, making it a Write-category action. Severity is medium because misconfigured system variables could corrupt drawing output, affect batch processing pipelines, or render files unusable until corrected—but changes are reversible and don't destructively delete data.

From the tool's definition Tool name 'system_set_variable' combined with description 'Set an AutoCAD system variable' indicates modification of configuration values.

Risk signalsAdmin/system-level operation

Documented attack patterns abuse exactly the kind of access system_set_variable gives an agent:

POLICY

How to control system_set_variable

PolicyLayer is an MCP gateway — it sits between your AI agents and AutoCAD MCP Pro, and nothing reaches the server without passing your rules. This is the rule we recommend for system_set_variable:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "system_set_variable": {
      "limits": [
        {
          "counter": "system_set_variable_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

system_set_variable 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.

Create a free account and register AutoCAD MCP Pro — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More AutoCAD MCP Pro tools

Destructive construction_clear Delete every entity on the CONSTRUCTION layer. Idempotent. Destructive drawing_purge Purge all unused objects (layers, blocks, linetypes, styles) from the drawing. Destructive entity_delete Permanently delete an entity by its handle. Destructive entity_delete_many Delete multiple entities in one call. Returns count of deleted entities. Destructive layer_delete layer_delete Destructive block_explode block_explode Execute drawing_audit Run an integrity audit on the drawing to detect and fix errors. Execute system_run_command system_run_command

All 108 AutoCAD MCP Pro tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about system_set_variable

What does the system_set_variable tool do? +

Set an AutoCAD system variable (e.g. DIMSCALE, LTSCALE, MEASUREMENT). It is categorised as a Write tool in the AutoCAD MCP Pro MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on system_set_variable? +

Register the AutoCAD MCP Pro MCP server in PolicyLayer and add a rule for system_set_variable: 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 AutoCAD MCP Pro. Nothing to install.

What risk level is system_set_variable? +

system_set_variable is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit system_set_variable? +

Yes. Add a rate_limit block to the system_set_variable 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.

How do I block system_set_variable completely? +

Set action: deny in the PolicyLayer policy for system_set_variable. 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.

What MCP server provides system_set_variable? +

system_set_variable is provided by the AutoCAD MCP Pro MCP server (u-c4n/autocad-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every AutoCAD MCP Pro tool call.

Start from AutoCAD MCP Pro, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →