container_update · Homelab MCP: Risk & Policy

WHAT IT DOES

What container_update does on Homelab

AI agents invoke container_update to trigger actions in Homelab. 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 container_update needs a policy

This tool actively modifies running infrastructure by pulling new container images and restarting containers (or running docker compose up). It executes operational changes against live systems. While it doesn't permanently destroy data, it can disrupt running services, introduce breaking changes from new images, and affect production-like homelab workloads — making it high severity Execute.

From the tool's definition pull the latest image and restart it... uses docker compose pull + up instead

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

container_update Rate-limited

container_update 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": {
    "container_update": {
      "limits": [
        {
          "counter": "container_update_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 Homelab, so you can run agents against it safely.

FAQ

Questions about container_update

What does the container_update tool do? +

Update a specific container on the devbox: pull the latest image and restart it. If project_dir is provided, uses docker compose pull + up instead. It is categorised as a Execute tool in the Homelab MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on container_update? +

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

What risk level is container_update? +

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

Can I rate-limit container_update? +

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

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

container_update is provided by the Homelab MCP server (nainounen/homelab-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.