diff --git a/homeassistant/helpers/llm.py b/homeassistant/helpers/llm.py
index ce539de1fd7..5591c4a8aba 100644
--- a/homeassistant/helpers/llm.py
+++ b/homeassistant/helpers/llm.py
@@ -282,7 +282,7 @@ class AssistAPI(API):
         else:
             prompt.append(
                 "When a user asks to turn on all devices of a specific type, "
-                "ask user to specify an area."
+                "ask user to specify an area, unless there is only one device of that type."
             )
 
         if not tool_context.device_id or not async_device_supports_timers(
diff --git a/tests/helpers/test_llm.py b/tests/helpers/test_llm.py
index 63c1214dd6d..1c13d643928 100644
--- a/tests/helpers/test_llm.py
+++ b/tests/helpers/test_llm.py
@@ -432,7 +432,7 @@ async def test_assist_api_prompt(
 
     area_prompt = (
         "When a user asks to turn on all devices of a specific type, "
-        "ask user to specify an area."
+        "ask user to specify an area, unless there is only one device of that type."
     )
     api = await llm.async_get_api(hass, "assist", tool_context)
     assert api.api_prompt == (