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robbrad

homeassistant-mcp

by robbrad

Home Assistant MCP Server

A Model Context Protocol (MCP) server that lets AI assistants control Home Assistant. Built with Python and FastMCP.

Works with Claude, GPT-4, Cursor, Kiro, and any MCP-compatible client.

What it does

  • 40 tools covering lights, climate, covers, locks, media players, vacuums, fans, cameras, alarms, and more

  • BM25 tool search — LLMs discover tools on demand instead of receiving all 40 schemas upfront

  • MCP Resources for read-only entity, area, device, and service data

  • MCP Prompts for guided workflows (automation creation, troubleshooting, energy optimization)

  • Tool annotationsreadOnlyHint lets clients skip confirmation prompts for safe operations

  • Smart error log parsing — deduplicates and summarises HA error logs instead of dumping raw text

  • Context-aware responses — compact list responses, domain-filtered queries, progress reporting

  • Async throughout with TTL-based caching to reduce API load

Installation

No install needed. Just configure your MCP client:

{
  "mcpServers": {
    "homeassistant": {
      "command": "uvx",
      "args": ["homeassistant-mcp"],
      "env": {
        "HASS_HOST": "http://homeassistant.local:8123",
        "HASS_TOKEN": "your_long_lived_access_token_here"
      }
    }
  }
}

pip

pip install homeassistant-mcp
homeassistant-mcp

From source

git clone https://github.com/robbrad/homeassistant-mcp.git
cd homeassistant-mcp
python -m venv venv
source venv/bin/activate  # Windows: venv\Scripts\activate
pip install -e ".[dev]"
homeassistant-mcp

Configuration

The server needs two environment variables:

Variable

Description

HASS_HOST

Home Assistant URL, e.g. http://homeassistant.local:8123

HASS_TOKEN

Long-lived access token (how to create one)

Optional:

Variable

Default

Description

CACHE_TTL_STATES

30

Cache TTL for bulk state queries (seconds)

CACHE_TTL_ENTITY

10

Cache TTL for individual entity queries (seconds)

LOG_LEVEL

INFO

Logging level

These can be set via environment variables (as shown in the MCP client configs above) or in a .env file. See .env.example.

MCP Client Setup

Claude Desktop

Add to your config file:

  • macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

  • Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "homeassistant": {
      "command": "uvx",
      "args": ["homeassistant-mcp"],
      "env": {
        "HASS_HOST": "http://homeassistant.local:8123",
        "HASS_TOKEN": "your_token_here"
      }
    }
  }
}

Cursor / Kiro / Other MCP Clients

Same config format. Place it in your client's MCP configuration file (e.g. .cursor/mcp.json, .kiro/settings/mcp.json).

The server uses stdio transport, which is the standard for MCP.

How Tool Discovery Works

With 40 tools, the server uses BM25 search to keep the LLM's context lean. Instead of sending all 40 tool schemas upfront, the LLM sees 8 tools:

Tool

Purpose

discover_tools

Returns the full catalog of all 40 tools by category

states_control

Entity state management (list, get, set, delete)

list_devices

Device discovery with domain/area/floor filtering

call_service

Call any HA service directly

template_render

Render Jinja2 templates in HA context

error_log_get

Parsed and deduplicated error log summary

search_tools

BM25 search to find tools by description

call_tool

Execute a discovered tool by name

The LLM calls discover_tools() to see what's available, then search_tools(query="lights brightness") to get the full schema, then calls the tool directly.

All Tools

Device Control (16 tools)

Tool

Domain

Capabilities

lights_control

light

Brightness, color temp, RGB

climate_control

climate

HVAC modes, temperature, fan

switch_control

switch

On/off, bulk operations

cover_control

cover

Position, tilt, open/close

lock_control

lock

Lock/unlock with codes

media_player_control

media_player

Playback, volume, source

camera_control

camera

Snapshots, streams, motion detection

vacuum_control

vacuum

Start, dock, fan speed

fan_control

fan

Speed, oscillation, direction

alarm_control

alarm_control_panel

Arm/disarm modes

weather_control

weather

Conditions, daily/hourly forecasts

water_heater_control

water_heater

Temperature, modes

humidifier_control

humidifier

Humidity levels

siren_control

siren

Activation control

valve_control

valve

Open/close

lawn_mower_control

lawn_mower

Start, stop, dock

Automation & Scenes (3 tools)

Tool

Capabilities

automation_control

List, trigger, enable, disable, reload

scene_control

List, activate

script_control

List, execute with variables, reload

Input Helpers (5 tools)

Tool

Capabilities

input_boolean_control

Toggle on/off

input_number_control

Set value, increment, decrement

input_select_control

Select from options

input_text_control

Set text value

input_datetime_control

Set date/time

API & State (4 tools)

Tool

Capabilities

api_info

API status, HA config, loaded components

events_control

List event types, fire custom events

services_control

List services by domain, call services

states_control

List/get/set/delete entity states with filtering

History (3 tools)

Tool

Capabilities

history_query

State changes by entity + hours (not ISO timestamps)

logbook_query

Human-readable logbook entries

error_log_get

Parsed, deduplicated error summary with component counts

Specialized (5 tools)

Tool

Capabilities

calendar_access

List calendars, get events by date range

camera_proxy_get

Camera images with optional resize

config_check

Validate HA configuration

intent_handle

Process natural language intents

template_render

Render Jinja2 templates

General (4 tools)

Tool

Capabilities

list_devices

Filter by any domain, area, or floor

call_service

Call any HA service with custom data

send_notification

Send alerts via HA notification services

discover_tools

Full tool catalog for LLM discovery

MCP Resources

URI Pattern

Description

hass://entity/{entity_id}

Entity state and attributes

hass://area/{area_id}

Area entities (compact summaries)

hass://device/{device_id}

Device entities (compact summaries)

hass://services

All services organized by domain

hass://entity/{entity_id}/history

Entity history with pagination

Development

git clone https://github.com/robbrad/homeassistant-mcp.git
cd homeassistant-mcp
python -m venv venv
source venv/bin/activate
pip install -e ".[dev]"

# Run tests
pytest

# Format and lint
black src/ tests/
ruff check src/ tests/

# Type check
mypy src/

Publishing

Commits to main auto-publish to PyPI via GitHub Actions + python-semantic-release:

  • fix: commits → patch bump (3.1.0 → 3.1.1)

  • feat: commits → minor bump (3.1.0 → 3.2.0)

  • BREAKING CHANGE: → major bump (3.1.0 → 4.0.0)

Architecture

AI Assistant  <-->  MCP Server (FastMCP/stdio)  <-->  Home Assistant REST API
                         |
                   +-----+-----+
                   |           |
                 Tools      Cache
                 Layer      Layer
  • FastMCP Server handles MCP protocol over stdio with BM25 tool search

  • Home Assistant Client is an async httpx client with auth and connection pooling

  • Cache Layer provides TTL-based caching for states and entities

  • Tools Layer — 40 tools with annotations, tags, timeouts, and context logging

  • Resources — 5 read-only data endpoints with compact response envelopes

  • Prompts — 13 guided workflows for automation, troubleshooting, and optimization

License

MIT

A
license - permissive license
-
quality - not tested
B
maintenance

Maintenance

Maintainers
Response time
Release cycle
1Releases (12mo)

Resources

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