set_room_tiles · Loenn MCP: Risk & Policy

WHAT IT DOES

What set_room_tiles does on Loenn

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

WHY IT NEEDS A POLICY

Why set_room_tiles needs a policy

This tool creates or modifies map data (room tiles) in a reversible manner. While it alters the map file, the changes can be undone (reverted to previous versions or overwritten), making it Write rather than Destructive. The severity is high because misuse could corrupt significant portions of a map's playable geometry, but the effect is constrained to tile data within a single room and remains reversible.

From the tool's definition Tool name 'set_room_tiles' and description 'Set tile data for a room' indicates the tool modifies room tile data. The description explicitly states it sets/writes tile data, which is a reversible modification to map file structure.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_room_tiles Rate-limited

set_room_tiles 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_tiles": {
      "limits": [
        {
          "counter": "set_room_tiles_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 Loenn, so you can run agents against it safely.

FAQ

Questions about set_room_tiles

What does the set_room_tiles tool do? +

Set tile data for a room. Each row is a line of characters ('0'=air). It is categorised as a Write tool in the Loenn 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_tiles? +

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

What risk level is set_room_tiles? +

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

Can I rate-limit set_room_tiles? +

Yes. Add a rate_limit block to the set_room_tiles 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_tiles completely? +

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

set_room_tiles is provided by the Loenn MCP server (magedeline/loenn-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.