set_room

Server Excalidraw MCP Server val4evr/excalidraw-zephy

Category Write

Risk class Medium

Parameters 00 required

WHAT IT DOES

What set_room does on Excalidraw MCP Server

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

WHY IT NEEDS A POLICY

Why set_room needs a policy

This tool modifies the session state by changing which Excalidraw room is active, which is a write operation. It does not retrieve data (Read), execute arbitrary code (Execute), permanently delete anything (Destructive), or involve financial transactions (Financial).

From the tool's definition Tool description states it can 'Pin or switch the active Excalidraw room' and 'set the active room for this session', which modifies session state.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_room Rate-limited

set_room 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": {
    "set_room": {
      "limits": [
        {
          "counter": "set_room_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 Excalidraw MCP Server, so you can run agents against it safely.

FAQ

Questions about set_room

What does the set_room tool do? +

Pin or switch the active Excalidraw room for this session, or — with no arguments — report the current room. Pass a full roomUrl (https://<host>/r/<id>), or a bare roomId plus optional expressUrl for the server origin. Every other tool operates on the pinned room; you can also override a single call by passing roomUrl/roomId on that call. It is categorised as a Write tool in the Excalidraw 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 set_room? +

Register the Excalidraw MCP Server MCP server in PolicyLayer and add a rule for set_room: 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 Excalidraw MCP Server. Nothing to install.

What risk level is set_room? +

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

Can I rate-limit set_room? +

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

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

set_room is provided by the Excalidraw MCP Server MCP server (val4evr/excalidraw-zephy). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.