update_styleground · Loenn MCP: Risk & Policy

WHAT IT DOES

What update_styleground does on Loenn

AI agents use update_styleground 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 update_styleground needs a policy

Stylegrounds are visual/atmospheric elements in Celeste maps. Updating them modifies map data reversibly (edits can be undone by reloading or further edits), making this a Write operation rather than Destructive. The empty description lowers confidence slightly, but the name and server context are clear.

From the tool's definition Tool name 'update_styleground' indicates modification of styleground elements in Celeste map files. The server explicitly states it enables users to 'edit' .bin map files.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_styleground Rate-limited

update_styleground 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": {
    "update_styleground": {
      "limits": [
        {
          "counter": "update_styleground_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 update_styleground

What does the update_styleground tool do? +

update_styleground. 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 update_styleground? +

Register the Loenn MCP server in PolicyLayer and add a rule for update_styleground: 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 update_styleground? +

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

Can I rate-limit update_styleground? +

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

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

update_styleground 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.