brush_set_type · Open Brush MCP Server MCP: Risk & Policy

WHAT IT DOES

What brush_set_type does on Open Brush MCP Server

AI agents use brush_set_type 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 brush_set_type needs a policy

This tool changes the active brush type in Open Brush, which is a reversible configuration change. It modifies application state but doesn't delete data, execute code, or involve financial operations. Misuse has minimal blast radius as the brush type can easily be changed back.

From the tool's definition 'Change brush type' - modifies the brush setting in the 3D painting software

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

brush_set_type Rate-limited

brush_set_type 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": {
    "brush_set_type": {
      "limits": [
        {
          "counter": "brush_set_type_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 brush_set_type

What does the brush_set_type tool do? +

Change brush type. 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 brush_set_type? +

Register the Open Brush MCP Server MCP server in PolicyLayer and add a rule for brush_set_type: 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 brush_set_type? +

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

Can I rate-limit brush_set_type? +

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

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

brush_set_type 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.