guide_scale · Open Brush MCP Server MCP: Risk & Policy

WHAT IT DOES

What guide_scale does on Open Brush MCP Server

AI agents use guide_scale to create or update resources in Open Brush MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Open Brush MCP Server environment.

WHY IT NEEDS A POLICY

Why guide_scale needs a policy

This tool modifies the scale properties of a guide object in the 3D painting software. It changes existing data (scale of a guide) but is reversible (can be rescaled again), placing it in the Write category. The blast radius is low as it only affects a single guide's scale within the application.

From the tool's definition Sets non-uniform scale of a guide

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

guide_scale Rate-limited

guide_scale 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Open Brush MCP Server, so you can run agents against it safely.

FAQ

Questions about guide_scale

What does the guide_scale tool do? +

Sets non-uniform scale of a guide. It is categorised as a Write tool in the Open Brush MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on guide_scale? +

Register the Open Brush MCP Server MCP server in PolicyLayer and add a rule for guide_scale: 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 Open Brush MCP Server. Nothing to install.

What risk level is guide_scale? +

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

Can I rate-limit guide_scale? +

Yes. Add a rate_limit block to the guide_scale 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 guide_scale completely? +

Set action: deny in the PolicyLayer policy for guide_scale. 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 guide_scale? +

guide_scale is provided by the Open Brush MCP Server MCP server (moz411/openbrush-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.