run_jxa · Automator MCP: Risk & Policy

WHAT IT DOES

What run_jxa does on Automator

AI agents invoke run_jxa to trigger actions in Automator. 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 run_jxa needs a policy

run_jxa triggers real processes with real consequences. An agent gone sideways doesn't fire it once — it starts dozens of builds, sends mass notifications, or burns through compute before anyone looks up.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

run_jxa Rate-limited

run_jxa 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": {
    "run_jxa": {
      "limits": [
        {
          "counter": "run_jxa_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 Automator, so you can run agents against it safely.

FAQ

Questions about run_jxa

What does the run_jxa tool do? +

Execute JavaScript for Automation (JXA) code on macOS. It is categorised as a Execute tool in the Automator MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on run_jxa? +

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

What risk level is run_jxa? +

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

Can I rate-limit run_jxa? +

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

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

run_jxa is provided by the Automator MCP server (vetcoders/automator-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.