next_app · Ulanzi MCP: Risk & Policy

WHAT IT DOES

What next_app does on Ulanzi

AI agents invoke next_app to trigger actions in Ulanzi. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why next_app needs a policy

This tool triggers an external operation on a physical device (Ulanzi TC001 Smart Pixel Clock) — changing the currently displayed app. It's not a read (no data retrieval), not a write (no data creation/modification), but an execution of a device action via the AWTRIX3 HTTP API. The blast radius is low as it only affects display navigation on a smart clock.

From the tool's definition Switch to the next app in the display loop

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

next_app Rate-limited

next_app stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "next_app": {
      "limits": [
        {
          "counter": "next_app_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Ulanzi, so you can run agents against it safely.

FAQ

Questions about next_app

What does the next_app tool do? +

Switch to the next app in the display loop. It is categorised as a Execute tool in the Ulanzi MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on next_app? +

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

What risk level is next_app? +

next_app is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit next_app? +

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

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

next_app is provided by the Ulanzi MCP server (jelloeater/ulanzi-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.