farmbot_emergency_stop · Farmbot Agent MCP: Risk & Policy

WHAT IT DOES

What farmbot_emergency_stop does on Farmbot Agent

AI agents invoke farmbot_emergency_stop to trigger actions in Farmbot Agent. 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 farmbot_emergency_stop needs a policy

This tool executes an immediate control operation on physical hardware whose effects are triggered by the command itself, not reversible data modification. While the action can technically be undone by calling farmbot_unlock, the emergency stop is primarily an Execute operation (triggering external hardware behavior) rather than Write (data creation/modification) or Destructive (irreversible data loss).

From the tool's definition Tool description states it will 'immediately halt all FarmBot movement and lock the device' — this is a direct command that triggers hardware state changes (motor halt, device lock).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

farmbot_emergency_stop Rate-limited

farmbot_emergency_stop 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": {
    "farmbot_emergency_stop": {
      "limits": [
        {
          "counter": "farmbot_emergency_stop_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 Farmbot Agent, so you can run agents against it safely.

FAQ

Questions about farmbot_emergency_stop

What does the farmbot_emergency_stop tool do? +

EMERGENCY STOP — immediately halt all FarmBot movement and lock the device. Use when something is going wrong — a collision, unexpected behavior, or safety concern. The device will be locked until farmbot_unlock is called. This is the highest priority command and should always be available. It is categorised as a Execute tool in the Farmbot Agent MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on farmbot_emergency_stop? +

Register the Farmbot Agent MCP server in PolicyLayer and add a rule for farmbot_emergency_stop: 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 Farmbot Agent. Nothing to install.

What risk level is farmbot_emergency_stop? +

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

Can I rate-limit farmbot_emergency_stop? +

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

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

farmbot_emergency_stop is provided by the Farmbot Agent MCP server (kieranklaassen/farmbot-agent-cli-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.