brush_draw · Open Brush MCP Server MCP: Risk & Policy

WHAT IT DOES

What brush_draw does on Open Brush MCP Server

AI agents invoke brush_draw to trigger actions in Open Brush MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why brush_draw needs a policy

This tool executes an action in an external application (Open Brush) that produces a visual/creative output. It is not a simple data write to a database but rather triggers an operation in a running software environment. The blast radius is medium as misuse could corrupt or unintentionally alter an active 3D painting session, though effects are likely reversible within the application.

From the tool's definition 'Draws a straight line of specified length' — triggers an external drawing operation in Open Brush 3D painting software via HTTP API

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

brush_draw Rate-limited

brush_draw stays usable, but rate-capped — a runaway agent can't fire it dozens of times 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_draw": {
      "limits": [
        {
          "counter": "brush_draw_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-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_draw

What does the brush_draw tool do? +

Draws a straight line of specified length. It is categorised as a Execute tool in the Open Brush MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on brush_draw? +

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

brush_draw is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit brush_draw? +

Yes. Add a rate_limit block to the brush_draw 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_draw completely? +

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

brush_draw 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.