fritzctl — FRITZ!Home CLI & MCP Server

fritzctl controls FRITZ!DECT radiator thermostats directly via your FRITZ!Box — no cloud, no account, no internet required after first setup.

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Features

• Pure local control — authenticates against your FRITZ!Box via challenge-response; all traffic stays on your LAN
• Dual API support — Smart Home REST API (FRITZ!OS 8.20+) with automatic fallback to the legacy AHA XML API
• Rich CLI — human-readable tables or --json for scripts and pipes
• MCP server — expose your thermostats as tools to Claude or any MCP client
• Safety layer — enforces temperature bounds (8–28 °C), max delta (5 °C/operation), cooldown windows, and device lock/battery checks before every write
• Audit log — every write operation is recorded to ~/.config/fritz-local/audit.log
• Hub discovery — SSDP/UPnP M-SEARCH scan; no IP guessing needed
• Keyring integration — credentials stored securely in the OS keyring, never in plain text

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Installation

pip install fritzctl

Requires Python 3.14+.

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Quick start

1. Discover your FRITZ!Box

fritzctl discover

         FRITZ!Box Devices Found
┏━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━┓
┃ IP            ┃ URL                   ┃ Model           ┃
┡━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━┩
│ 192.168.178.1 │ http://192.168.178.1  │ FRITZ!Box 7590  │
└───────────────┴───────────────────────┴─────────────────┘

2. Authenticate and save credentials

fritzctl setup

Credentials are saved to the OS keyring and ~/.fritzhome/config.json. You only need to do this once.

3. Use it

fritzctl list
fritzctl status "Wohnzimmer"
fritzctl set-temp "Wohnzimmer" 21.5
fritzctl enable-boost "Kinderzimmer" --duration-seconds 600

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CLI reference

fritzctl [--json] <command> [args]

Command	Description
fritzctl discover	Scan the LAN for FRITZ!Box devices via SSDP/UPnP
fritzctl setup	Authenticate and persist credentials to keyring
fritzctl health	Check FRITZ!Box connectivity and API type
fritzctl list	List all thermostats and groups
fritzctl status [DEVICE]	Show temperature, battery, and lock state
fritzctl set-temp DEVICE TEMP	Set target temperature (°C) with safety check
fritzctl enable-boost DEVICE	Activate boost mode for a duration
fritzctl disable-window-open DEVICE	Cancel window-open mode early

All write commands support --dry-run (plan only, no execution) and --no-confirm (skip interactive prompt).

Exit codes

Code	Meaning
0	success
1	error (authentication, network, safety violation)

Safety guardrails

Every write command is checked by the SafetyPolicyEngine before execution:

• Temperature must be between 8 °C and 28 °C
• Change cannot exceed ±5 °C in a single operation
• Device must be online, unlocked, and have battery > 10 %
• A cooldown window prevents repeat writes in quick succession

[!NOTE] Device names or AIns are both accepted as identifiers. If a device is temporarily offline, the local cache (~/.fritzhome/config.json) is used to resolve names to AIns.

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MCP server

fritzctl ships with an MCP server that exposes your thermostats as tools for Claude or any MCP-compatible client.

[!WARNING] Write tools are disabled by default. Set FRITZ_MCP_ALLOW_WRITES=true to enable set_heater_temperature, enable_boost, and disable_window_open.

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "fritz": {
      "command": "fritzctl-mcp",
      "args": [],
      "env": {
        "FRITZ_BOX_URL": "http://192.168.178.1",
        "FRITZ_MCP_ALLOW_WRITES": "true"
      }
    }
  }
}

VS Code (agent mode)

{
  "mcp": {
    "servers": {
      "fritz": {
        "command": "fritzctl-mcp",
        "type": "stdio",
        "env": {
          "FRITZ_BOX_URL": "http://192.168.178.1",
          "FRITZ_MCP_ALLOW_WRITES": "true"
        }
      }
    }
  }
}

Available MCP tools

list_heaters · get_heater_status · get_group_status · set_heater_temperature · enable_boost · disable_window_open

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Configuration

Credentials and URL are stored in ~/.fritzhome/config.json (non-sensitive) and the OS keyring (password). You can also use environment variables:

Variable	Description
FRITZ_BOX_URL	FRITZ!Box base URL (default: http://192.168.178.1)
FRITZ_BOX_USERNAME	Username (leave unset for password-only boxes)
FRITZ_BOX_PASSWORD	Password fallback when keyring is unavailable
FRITZ_MCP_ALLOW_WRITES	Set to true to enable write tools in the MCP server

Precedence: keyring / config file > env var > default.

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Python library

import asyncio
from fritzctl.avm.clients import fritz_client_context


async def main() -> None:
    async with fritz_client_context() as client:
        devices = await client.list_devices()
        for d in devices:
            print(f"{d.name}: {d.current_temp:.1f}°C → {d.target_temp:.1f}°C")

        await client.set_temperature("12345 67890", 21.0)


asyncio.run(main())

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Development

git clone https://github.com/jenreh/fritzhome-py
cd fritzhome-py
uv sync
task test     # pytest with coverage
task lint     # ruff + mypy
task format   # ruff format

[!NOTE] Tests use pytest-httpserver to mock the FRITZ!Box HTTP API — no real hardware required.