canvas_open · Whiteboard MCP: Risk & Policy

WHAT IT DOES

What canvas_open does on Whiteboard

AI agents invoke canvas_open to trigger actions in Whiteboard. 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 canvas_open needs a policy

This tool executes a browser action (opening a canvas), which constitutes an external operation whose effects depend on arguments. It falls under Execute as it triggers a real-time browser interaction rather than simply reading or writing data.

From the tool's definition 'Open a canvas in the browser' — triggers an external browser operation

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

canvas_open Rate-limited

canvas_open 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": {
    "canvas_open": {
      "limits": [
        {
          "counter": "canvas_open_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 Whiteboard, so you can run agents against it safely.

FAQ

Questions about canvas_open

What does the canvas_open tool do? +

Open a canvas in the browser. It is categorised as a Execute tool in the Whiteboard MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on canvas_open? +

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

What risk level is canvas_open? +

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

Can I rate-limit canvas_open? +

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

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

canvas_open is provided by the Whiteboard MCP server (kamiazya/whiteboard). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.