app_start

Start an installed app by its ID.

SERVERTruenas SOURCEspranab/truenas-mcp

High RISK CLASS

Category Execute

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/spranab-truenas-mcp/app-start.md

WHAT IT DOES

What app_start does on Truenas

AI agents invoke app_start to trigger actions in Truenas. 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.

RISK

Why app_start is rated High

Starting an application is an Execute action because it initiates code/service execution whose side effects depend on the argument (the app ID). Unlike Read operations (which only retrieve data) or Write operations (which reversibly create/modify data), starting an app runs external processes with real system impact.

From the tool's definition Tool performs 'Start an installed app by its ID' — this is an action that triggers execution of an external application or service, whose effects depend on which app is specified as an argument.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs app_start safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Truenas, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For app_start, this is the rule to start with:

app_start Rate-limited

app_start 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": {
    "app_start": {
      "limits": [
        {
          "counter": "app_start_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Truenas, apply this rule, and every app_start call is checked against it from then on.

FAQ

Questions about app_start

What does the app_start tool do? +

Start an installed app by its ID. 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_start? +

Register the Truenas MCP server in PolicyLayer and add a rule for app_start: 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_start? +

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

Can I rate-limit app_start? +

Yes. Add a rate_limit block to the app_start 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_start completely? +

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

app_start 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.

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