app_pull_images

THE RISK

High Risk

Why app_pull_images needs a policy

Pulling Docker images triggers an external network operation that fetches and stores container images from a remote registry. This is not a simple read (it modifies local state by downloading/storing images) nor a pure write (it executes an external fetch operation with side effects dependent on remote registry state).

From the tool's definition Pull the latest Docker images for a specific app

Documented attack patterns abuse exactly the kind of access app_pull_images gives an agent:

POLICY

How to control app_pull_images

PolicyLayer is an MCP gateway — it sits between your AI agents and Truenas, and nothing reaches the server without passing your rules. This is the rule we recommend for app_pull_images:

policy.json

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

app_pull_images 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.

Create a free account and register Truenas — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

High-risk tools in Truenas → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
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FAQ

Questions about app_pull_images

What does the app_pull_images tool do? +

Pull the latest Docker images for a specific app. It is categorised as a Execute tool in the Truenas MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on app_pull_images? +

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

What risk level is app_pull_images? +

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

Can I rate-limit app_pull_images? +

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

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

app_pull_images is provided by the Truenas MCP server (spranab/truenas-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Truenas tool call.

Start from Truenas, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →