draw_rect · Paint MCP: Risk & Policy

WHAT IT DOES

What draw_rect does on Paint MCP

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

WHY IT NEEDS A POLICY

Why draw_rect needs a policy

This tool writes/renders a rectangle onto the drawing canvas. It creates visual data on the canvas, which is a reversible write operation (the canvas can be cleared). No code execution, deletion, or financial activity is involved.

From the tool's definition Draw a rectangle. (x, y) is the top-left corner.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

draw_rect Rate-limited

draw_rect 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": {
    "draw_rect": {
      "limits": [
        {
          "counter": "draw_rect_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 Paint MCP, so you can run agents against it safely.

FAQ

Questions about draw_rect

What does the draw_rect tool do? +

Draw a rectangle. (x, y) is the top-left corner. It is categorised as a Write tool in the Paint MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on draw_rect? +

Register the Paint MCP server in PolicyLayer and add a rule for draw_rect: 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 Paint MCP. Nothing to install.

What risk level is draw_rect? +

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

Can I rate-limit draw_rect? +

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

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

draw_rect is provided by the Paint MCP server (joeyballentine/paint-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.