Remove entity state from mcp-server prompt (#137126)

* Create a stateless assist API for MCP server

* Update stateless API

* Fix areas in exposed entity fields

* Add tests that verify areas are returned

* Revert the getstate intent

* Revert whitespace change

* Revert whitespace change

* Revert method name changes to avoid breaking openai and google tests

homeassistant/components/mcp_server/__init__.py

@@ -6,7 +6,7 @@ from homeassistant.core import HomeAssistant
 from homeassistant.helpers import config_validation as cv
 from homeassistant.helpers.typing import ConfigType
 
-from . import http
+from . import http, llm_api
 from .const import DOMAIN
 from .session import SessionManager
 from .types import MCPServerConfigEntry
@@ -25,6 +25,7 @@ CONFIG_SCHEMA = cv.config_entry_only_config_schema(DOMAIN)
 async def async_setup(hass: HomeAssistant, config: ConfigType) -> bool:
     """Set up the Model Context Protocol component."""
     http.async_register(hass)
+    llm_api.async_register_api(hass)
     return True
 
 

homeassistant/components/mcp_server/config_flow.py

@@ -16,7 +16,7 @@ from homeassistant.helpers.selector import (
     SelectSelectorConfig,
 )
 
-from .const import DOMAIN
+from .const import DOMAIN, LLM_API, LLM_API_NAME
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -33,6 +33,12 @@ class ModelContextServerProtocolConfigFlow(ConfigFlow, domain=DOMAIN):
     ) -> ConfigFlowResult:
         """Handle the initial step."""
         llm_apis = {api.id: api.name for api in llm.async_get_apis(self.hass)}
+        if LLM_API not in llm_apis:
+            # MCP server component is not loaded yet, so make the LLM API a choice.
+            llm_apis = {
+                LLM_API: LLM_API_NAME,
+                **llm_apis,
+            }
 
         if user_input is not None:
             return self.async_create_entry(

homeassistant/components/mcp_server/const.py

@@ -2,3 +2,5 @@
 
 DOMAIN = "mcp_server"
 TITLE = "Model Context Protocol Server"
+LLM_API = "stateless_assist"
+LLM_API_NAME = "Stateless Assist"

homeassistant/components/mcp_server/llm_api.py

@@ -0,0 +1,48 @@
+"""LLM API for MCP Server."""
+
+from homeassistant.core import HomeAssistant, callback
+from homeassistant.helpers import llm
+from homeassistant.util import yaml as yaml_util
+
+from .const import LLM_API, LLM_API_NAME
+
+EXPOSED_ENTITY_FIELDS = {"name", "domain", "description", "areas", "names"}
+
+
+def async_register_api(hass: HomeAssistant) -> None:
+    """Register the LLM API."""
+    llm.async_register_api(hass, StatelessAssistAPI(hass))
+
+
+class StatelessAssistAPI(llm.AssistAPI):
+    """LLM API for MCP Server that provides the Assist API without state information in the prompt.
+
+    Syncing the state information is possible, but may put unnecessary load on
+    the system so we are instead providing the prompt without entity state. Since
+    actions don't care about the current state, there is little quality loss.
+    """
+
+    def __init__(self, hass: HomeAssistant) -> None:
+        """Initialize the StatelessAssistAPI."""
+        super().__init__(hass)
+        self.id = LLM_API
+        self.name = LLM_API_NAME
+
+    @callback
+    def _async_get_exposed_entities_prompt(
+        self, llm_context: llm.LLMContext, exposed_entities: dict | None
+    ) -> list[str]:
+        """Return the prompt for the exposed entities."""
+        prompt = []
+
+        if exposed_entities:
+            prompt.append(
+                "An overview of the areas and the devices in this smart home:"
+            )
+            entities = [
+                {k: v for k, v in entity_info.items() if k in EXPOSED_ENTITY_FIELDS}
+                for entity_info in exposed_entities.values()
+            ]
+            prompt.append(yaml_util.dump(list(entities)))
+
+        return prompt

homeassistant/helpers/llm.py

@@ -326,12 +326,21 @@ class AssistAPI(API):
     def _async_get_api_prompt(
         self, llm_context: LLMContext, exposed_entities: dict | None
     ) -> str:
-        """Return the prompt for the API."""
         if not exposed_entities:
             return (
                 "Only if the user wants to control a device, tell them to expose entities "
                 "to their voice assistant in Home Assistant."
             )
+        return "\n".join(
+            [
+                *self._async_get_preable(llm_context),
+                *self._async_get_exposed_entities_prompt(llm_context, exposed_entities),
+            ]
+        )
+
+    @callback
+    def _async_get_preable(self, llm_context: LLMContext) -> list[str]:
+        """Return the prompt for the API."""
 
         prompt = [
             (
@@ -371,13 +380,22 @@ class AssistAPI(API):
         ):
             prompt.append("This device is not able to start timers.")
 
+        return prompt
+
+    @callback
+    def _async_get_exposed_entities_prompt(
+        self, llm_context: LLMContext, exposed_entities: dict | None
+    ) -> list[str]:
+        """Return the prompt for the API for exposed entities."""
+        prompt = []
+
         if exposed_entities:
             prompt.append(
                 "An overview of the areas and the devices in this smart home:"
             )
             prompt.append(yaml_util.dump(list(exposed_entities.values())))
 
-        return "\n".join(prompt)
+        return prompt
 
     @callback
     def _async_get_tools(

tests/components/mcp_server/conftest.py

@@ -5,10 +5,9 @@ from unittest.mock import AsyncMock, patch
 
 import pytest
 
-from homeassistant.components.mcp_server.const import DOMAIN
+from homeassistant.components.mcp_server.const import DOMAIN, LLM_API
 from homeassistant.const import CONF_LLM_HASS_API
 from homeassistant.core import HomeAssistant
-from homeassistant.helpers import llm
 
 from tests.common import MockConfigEntry
 
@@ -28,7 +27,7 @@ def mock_config_entry(hass: HomeAssistant) -> MockConfigEntry:
     config_entry = MockConfigEntry(
         domain=DOMAIN,
         data={
-            CONF_LLM_HASS_API: llm.LLM_API_ASSIST,
+            CONF_LLM_HASS_API: LLM_API,
         },
     )
     config_entry.add_to_hass(hass)

tests/components/mcp_server/test_http.py

@@ -20,7 +20,11 @@ from homeassistant.components.mcp_server.http import MESSAGES_API, SSE_API
 from homeassistant.config_entries import ConfigEntryState
 from homeassistant.const import CONF_LLM_HASS_API, STATE_OFF, STATE_ON
 from homeassistant.core import HomeAssistant
-from homeassistant.helpers import device_registry as dr, entity_registry as er
+from homeassistant.helpers import (
+    area_registry as ar,
+    device_registry as dr,
+    entity_registry as er,
+)
 from homeassistant.setup import async_setup_component
 
 from tests.common import MockConfigEntry, setup_test_component_platform
@@ -45,6 +49,11 @@ INITIALIZE_MESSAGE = {
 }
 EVENT_PREFIX = "event: "
 DATA_PREFIX = "data: "
+EXPECTED_PROMPT_SUFFIX = """
+- names: Kitchen Light
+  domain: light
+  areas: Kitchen
+"""
 
 
 @pytest.fixture
@@ -59,11 +68,13 @@ async def mock_entities(
     hass: HomeAssistant,
     device_registry: dr.DeviceRegistry,
     entity_registry: er.EntityRegistry,
+    area_registry: ar.AreaRegistry,
     setup_integration: None,
 ) -> None:
     """Fixture to expose entities to the conversation agent."""
-    entity = MockLight("kitchen", STATE_OFF)
+    entity = MockLight("Kitchen Light", STATE_OFF)
     entity.entity_id = TEST_ENTITY
+    entity.unique_id = "test-light-unique-id"
     setup_test_component_platform(hass, LIGHT_DOMAIN, [entity])
 
     assert await async_setup_component(
@@ -71,6 +82,9 @@ async def mock_entities(
         LIGHT_DOMAIN,
         {LIGHT_DOMAIN: [{"platform": "test"}]},
     )
+    await hass.async_block_till_done()
+    kitchen = area_registry.async_get_or_create("Kitchen")
+    entity_registry.async_update_entity(TEST_ENTITY, area_id=kitchen.id)
 
     async_expose_entity(hass, CONVERSATION_DOMAIN, TEST_ENTITY, True)
 
@@ -320,7 +334,7 @@ async def test_mcp_tool_call(
     async with mcp_session(mcp_sse_url, hass_supervisor_access_token) as session:
         result = await session.call_tool(
             name="HassTurnOn",
-            arguments={"name": "kitchen"},
+            arguments={"name": "kitchen light"},
         )
 
     assert not result.isError
@@ -370,8 +384,11 @@ async def test_prompt_list(
 
     assert len(result.prompts) == 1
     prompt = result.prompts[0]
-    assert prompt.name == "Assist"
-    assert prompt.description == "Default prompt for the Home Assistant LLM API Assist"
+    assert prompt.name == "Stateless Assist"
+    assert (
+        prompt.description
+        == "Default prompt for the Home Assistant LLM API Stateless Assist"
+    )
 
 
 async def test_prompt_get(
@@ -383,13 +400,17 @@ async def test_prompt_get(
     """Test the get prompt endpoint."""
 
     async with mcp_session(mcp_sse_url, hass_supervisor_access_token) as session:
-        result = await session.get_prompt(name="Assist")
+        result = await session.get_prompt(name="Stateless Assist")
 
-    assert result.description == "Default prompt for the Home Assistant LLM API Assist"
+    assert (
+        result.description
+        == "Default prompt for the Home Assistant LLM API Stateless Assist"
+    )
     assert len(result.messages) == 1
     assert result.messages[0].role == "assistant"
     assert result.messages[0].content.type == "text"
     assert "When controlling Home Assistant" in result.messages[0].content.text
+    assert result.messages[0].content.text.endswith(EXPECTED_PROMPT_SUFFIX)
 
 
 async def test_get_unknwon_prompt(