Home Assistant MCP Server

Instructions

Implementation Reference

• src/index.ts:207-229 (handler)

  Switch case handler for 'call_service' tool that prepares service data and calls haClient.callService

  case "call_service": {
    const serviceData: any = {};
    if (args?.entity_id) {
      serviceData.entity_id = args.entity_id;
    }
    if (args?.data) {
      Object.assign(serviceData, args.data);
    }
  
    const result = await haClient.callService(
      args?.domain as string,
      args?.service as string,
      serviceData
    );
    return {
      content: [
        {
          type: "text",
          text: JSON.stringify(result, null, 2),
        },
      ],
    };
  }

• src/index.ts:127-152 (registration)

  Tool registration for 'call_service' including name, description, and input schema

  {
    name: "call_service",
    description: "Call a Home Assistant service (e.g., turn on a light, set climate)",
    inputSchema: {
      type: "object",
      properties: {
        domain: {
          type: "string",
          description: "Service domain (e.g., 'light', 'switch', 'climate')",
        },
        service: {
          type: "string",
          description: "Service name (e.g., 'turn_on', 'turn_off', 'set_temperature')",
        },
        entity_id: {
          type: "string",
          description: "Target entity ID",
        },
        data: {
          type: "object",
          description: "Additional service data (e.g., brightness, temperature)",
        },
      },
      required: ["domain", "service"],
    },
  },

• src/index.ts:58-62 (helper)

  HomeAssistantClient method that performs the actual service call via the HA API

  async callService(domain: string, service: string, data: any = {}) {
    return this.fetch(`services/${domain}/${service}`, {
      method: "POST",
      body: JSON.stringify(data),
    });