open_document · AI-Canvas MCP Server MCP: Risk & Policy

WHAT IT DOES

What open_document does on AI-Canvas MCP Server

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

WHY IT NEEDS A POLICY

Why open_document needs a policy

Creating new design documents is a reversible modification operation that adds state to the system. While opening existing documents would be Read-only, the explicit mention of document creation capability elevates this to Write.

From the tool's definition Tool description states it can "create a new one" design document, which is a write operation that modifies the document store. The ability to open existing documents is Read, but the creation capability makes this primarily a Write action.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

open_document Rate-limited

open_document 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": {
    "open_document": {
      "limits": [
        {
          "counter": "open_document_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 AI-Canvas MCP Server, so you can run agents against it safely.

FAQ

Questions about open_document

What does the open_document tool do? +

Open a design document from a file path or create a new one. It is categorised as a Write tool in the AI-Canvas 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 open_document? +

Register the AI-Canvas MCP Server MCP server in PolicyLayer and add a rule for open_document: 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 AI-Canvas MCP Server. Nothing to install.

What risk level is open_document? +

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

Can I rate-limit open_document? +

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

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

open_document is provided by the AI-Canvas MCP Server MCP server (laoluojuhai/ai-canvas). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.