pane_set_metadata · Wmux MCP: Risk & Policy

WHAT IT DOES

What pane_set_metadata does on Wmux

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

WHY IT NEEDS A POLICY

Why pane_set_metadata needs a policy

This tool creates or modifies metadata attributes on a pane object — a classic Write operation. It is reversible (metadata can be overwritten or cleared), has no destructive or executable side effects, and operates entirely within the pane's state management. Severity is low because metadata attachment poses minimal risk even if misused by an AI agent.

From the tool's definition Tool attaches and modifies descriptive metadata (label/status + custom k/v) to a pane. The description explicitly mentions 'deep-merged' behavior, indicating reversible modification of metadata state.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

pane_set_metadata Rate-limited

pane_set_metadata 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": {
    "pane_set_metadata": {
      "limits": [
        {
          "counter": "pane_set_metadata_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 Wmux, so you can run agents against it safely.

FAQ

Questions about pane_set_metadata

What does the pane_set_metadata tool do? +

Attach descriptive metadata (label/status + custom k/v) to a leaf pane in the calling workspace. The custom map is deep-merged when mergeMode=. It is categorised as a Write tool in the Wmux MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on pane_set_metadata? +

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

What risk level is pane_set_metadata? +

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

Can I rate-limit pane_set_metadata? +

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

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

pane_set_metadata is provided by the Wmux MCP server (openwong2kim/wmux). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.