diff --git a/homeassistant/components/openai_conversation/entity.py b/homeassistant/components/openai_conversation/entity.py
index 9c1e77be7d3..64439c8a9c1 100644
--- a/homeassistant/components/openai_conversation/entity.py
+++ b/homeassistant/components/openai_conversation/entity.py
@@ -92,6 +92,8 @@ MAX_TOOL_ITERATIONS = 10
 def _adjust_schema(schema: dict[str, Any]) -> None:
     """Adjust the schema to be compatible with OpenAI API."""
     if schema["type"] == "object":
+        schema.setdefault("strict", True)
+        schema.setdefault("additionalProperties", False)
         if "properties" not in schema:
             return
 
@@ -125,8 +127,6 @@ def _format_structured_output(
 
     _adjust_schema(result)
 
-    result["strict"] = True
-    result["additionalProperties"] = False
     return result
 
 
diff --git a/tests/components/openai_conversation/test_entity.py b/tests/components/openai_conversation/test_entity.py
index 58187bd63e9..c24cb5b3d79 100644
--- a/tests/components/openai_conversation/test_entity.py
+++ b/tests/components/openai_conversation/test_entity.py
@@ -63,6 +63,8 @@ async def test_format_structured_output() -> None:
                         "item_value",
                     ],
                     "type": "object",
+                    "additionalProperties": False,
+                    "strict": True,
                 },
                 "type": "array",
             },