farmbot_write_pin · Farmbot Agent MCP: Risk & Policy

WHAT IT DOES

What farmbot_write_pin does on Farmbot Agent

AI agents use farmbot_write_pin to create or update resources in Farmbot Agent — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Farmbot Agent environment.

WHY IT NEEDS A POLICY

Why farmbot_write_pin needs a policy

This tool modifies hardware state by writing values to GPIO pins, which is a reversible operation (a pin can be set to a different value). It does not delete data (Destructive), execute arbitrary code (Execute), or move money (Financial).

From the tool's definition Tool name 'farmbot_write_pin' and description 'Write a value to a GPIO pin' and 'Sets a pin to a specific value.' These phrases directly indicate data/state modification of hardware pins.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

farmbot_write_pin Rate-limited

farmbot_write_pin stays usable, but capped — an agent stuck in a loop can't make hundreds of changes 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_write_pin": {
      "limits": [
        {
          "counter": "farmbot_write_pin_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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_write_pin

What does the farmbot_write_pin tool do? +

Write a value to a GPIO pin on the FarmBot. Sets a pin to a specific value. Use digital mode (0 or 1) for on/off control of peripherals like the water valve or vacuum pump. Use analog mode (0-255) for variable output like LED brightness. It is categorised as a Write tool in the Farmbot Agent MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on farmbot_write_pin? +

Register the Farmbot Agent MCP server in PolicyLayer and add a rule for farmbot_write_pin: 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_write_pin? +

farmbot_write_pin is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit farmbot_write_pin? +

Yes. Add a rate_limit block to the farmbot_write_pin 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_write_pin completely? +

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

farmbot_write_pin 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.