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Model Context Protocol Server

The Model Context Protocol is an open protocol that standardizes how applications provide context to LLMs. The Model Context Protocol Server (MCP) integration enables using Home Assistant to provide context for MCP LLM Client Applications. For example, you can expose your Google Tasks To-do list as a tool for Claude Desktop.

Controlling Home Assistant is done by providing MCP clients access to the Assist API of Home Assistant. You can control what devices and entities it can access from the exposed entities page.

Prerequisites

  • You need an MCP client LLM Application such as Claude for Desktop.
  • Since most clients do not support native remote servers, you need an additional local MCP server remote gateway.

For detailed configuration instructions, refer to the Client configuration section.

Configuration

To add the Model Context Protocol Server service to your Home Assistant instance, use this My button:

Manual configuration steps

If the above My button doesn’t work, you can also perform the following steps manually:

  • Browse to your Home Assistant instance.

  • Go to Settings > Devices & Services.

  • In the bottom right corner, select the Add Integration button.

  • From the list, select Model Context Protocol Server.

  • Follow the instructions on screen to complete the setup.

Configuration options

The integration provides the following configuration options:

Control Home Assistant

The API to use to expose tools over the Model Context Protocol. It is recommended to use Stateless Assist which is a version of the Assist API where the prompt does not contain any state information. Clients can only control or provide information about entities that are exposed to it.

Architecture overview

This integration can provide similar functionality as other LLM-based conversation agents (for example Anthropic, Google Generative AI, Ollama, Open AI). In those conversation agents, Home Assistant is the client and prepares the available tools and passes them into the LLM with a prompt.

The Model Context Protocol follows a different pattern: An LLM application acts as a client and can connect to multiple MCP servers to provide context. See the Model Context Protocol Introduction for more details.

The Home Assistant Model Context Protocol Server integration implements the Server-Sent Events (SSE) transport allowing streaming client-to-server communication. Most MCP clients today only support stdio transport, and directly run an MCP server as a local command line tool. You can use an MCP proxy server like mcp-proxy to act as a gateway to the Home Assistant MCP SSE server.

Client configuration

The Model Context Protocol specification does not yet define standards for authentication and connecting to remote servers. These are a work in progress and this configuration will likely change in the near future.

Access control

For now, we can use Long-lived access token to control access to the API.

  1. Visit your account profile settings, under the Security tab. .

  2. Create a Long-lived access token

  3. Copy the access token to use when configuring the MCP client LLM application.

For more information about Authentication in Home Assistant, refer to the Authentication documentation.

Example: Claude for Desktop

See MCP Quickstart: For Claude Desktop Users for a detailed guide on using Claude for Desktop with an MCP server. It is recommended to get the example server working first before using the Home Assistant MCP Server.

Claude for Desktop currently only supports local MCP servers using the stdio transport, run as a local command line tool. You can use a local MCP proxy server to allow Claude for Desktop to access Home Assistant using the SSE transport.

  1. Download Claude for Desktop.
  2. Install mcp-proxy following the instructions in the README. For example, uv tool install git+https://github.com/sparfenyuk/mcp-proxy.
  3. Open the configuration file. Visit Settings… and on the Developer tab, select Edit Config. which will edit claude_desktop_config.json. The full file location depends on your operating system (macOS or Windows).
  4. Add a new MCP server to the JSON file. You need to set the SSE_URL to the URL you use to connect to Home Assistant with the path /mcp_server/sse. You will also need to set API_ACCESS_TOKEN to the long live access token created above in the access control instructions 
    {
  "mcpServers": {
    "Home Assistant": {
      "command": "mcp-proxy",
      "env": {
        "SSE_URL": "http://localhost:8123/mcp_server/sse",
        "API_ACCESS_TOKEN": "<your_access_token_here>"
      }
    }
  }
}
  5. Restart Claude.
  6. You will see a connection icon if things are set up correctly. Clicking the connection icon will show enabled MCP servers such as Home Assistant.
  7. Select the prompt provided by Home Assistant.
  8. You can then use Claude to control Home Assistant similar to how you control Home Assistant through the Voice Assistant. Claude wil ask you for permission before calling any tools.

Screenshot of Claude for Desktop adding an item to a Home Assistant To-do list

Supported functionality

Tools

MCP Tools enable LLMs to perform actions through Home Assistant. The tools used by the configured LLM API are exposed.

Prompts

The MCP Prompts provided inform LLMs how to call the tools. The tools used by the configured LLM API are exposed.

It is recommended to use the Stateless Assist API since the prompt does not contain any state information, which will be incorrect after any actions are performed.

Known Limitations

The Home Assistant Model Context Protocol integration currently only supports a subset of MCP features:

Feature Supported by Home Assistant
Prompts ✅
Tools ✅
Resources ❌
Sampling ❌
Notifications ❌

Home Assistant does not yet provide built-in tools that can fetch device state.

Troubleshooting

This section has troubleshooting information for Claude for Desktop since it is the primary client. Also see Debugging in Claude Desktop.

LLM client cannot connect to Home Assistant MCP server

Symptom: Failed to start MCP server: Could not start MCP server Home Assistant

When trying to configure a client like Claude for Desktop to talk to Home Assistant, the app shows a message like “Failed to start MCP server: Could not start MCP server Home Assistant”

Description

This means that the local MCP server mcp-proxy could not start.

Resolution

Verify the command line arguments in the claude_desktop_config.json are correct. You may try to run the command manually to verify that the command can be found.

Symptom: “MCP server Home Assistant disconnected” or “Could not attach to MCP server Home Assistant”

When trying to configure a client like Claude Desktop to talk to Home Assistant, the app shows a message like “MCP server Home Assistant disconnected” or “Could not attach to MCP server Home Assistant”.

Description

This means the MCP server has started, however the MCP server is having trouble communicating with Home Assistant, or the MCP server in Home Assistant is not configured.

Resolution

To understand the root cause, first check debug logs on the client. For example in Claude for Desktop:

  1. Visit Settings….
  2. Select Developer.
  3. Select the Home Assistant MCP server.
  4. Select Open Logs Folder.
  5. View mcp-server-Home Assistant.log. These are known problems and their resolution:
    • Client error '404 Not Found' for url 'http://localhost:8123/mcp_server/sse': this means the MCP Server integration is not configured in Home Assistant.
    • Client error '401 Unauthorized' for url 'http://localhost:8123/mcp_server/sse': this means that the long live access token is not correct. …

Remove integration

This integration can be removed by following these steps:

To remove an integration instance from Home Assistant

  1. Go to Settings > Devices & services and select the integration card.
  2. From the list of devices, select the integration instance you want to remove.
  3. Next to the entry, select the three-dot menu. Then, select Delete.

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