diff --git a/litellm/llms/anthropic/experimental_pass_through/responses_adapters/transformation.py b/litellm/llms/anthropic/experimental_pass_through/responses_adapters/transformation.py
index 1a052f457c5..0cf6d15c65b 100644
--- a/litellm/llms/anthropic/experimental_pass_through/responses_adapters/transformation.py
+++ b/litellm/llms/anthropic/experimental_pass_through/responses_adapters/transformation.py
@@ -198,14 +198,16 @@ class LiteLLMAnthropicToResponsesAPIAdapter:
     @staticmethod
     def translate_tool_choice_to_responses_api(
         tool_choice: AnthropicMessagesToolChoice,
-    ) -> Dict[str, Any]:
+    ) -> Union[str, Dict[str, Any]]:
         """Convert Anthropic tool_choice to Responses API tool_choice."""
         tc_type = tool_choice.get("type")
         if tc_type == "any":
-            return {"type": "required"}
+            return "required"
+        elif tc_type == "none":
+            return "none"
         elif tc_type == "tool":
             return {"type": "function", "name": tool_choice.get("name", "")}
-        return {"type": "auto"}
+        return "auto"
 
     @staticmethod
     def translate_context_management_to_responses_api(
diff --git a/tests/test_litellm/llms/anthropic/experimental_pass_through/responses_adapters/test_responses_adapters_transformation.py b/tests/test_litellm/llms/anthropic/experimental_pass_through/responses_adapters/test_responses_adapters_transformation.py
index 14e872485ec..7555d04e648 100644
--- a/tests/test_litellm/llms/anthropic/experimental_pass_through/responses_adapters/test_responses_adapters_transformation.py
+++ b/tests/test_litellm/llms/anthropic/experimental_pass_through/responses_adapters/test_responses_adapters_transformation.py
@@ -587,14 +587,20 @@ class TestTranslateToolChoiceToResponsesAPI:
     """Anthropic tool_choice -> Responses API tool_choice."""
 
     def test_auto_maps_to_auto(self):
-        assert _ADAPTER.translate_tool_choice_to_responses_api({"type": "auto"}) == {
-            "type": "auto"
-        }
+        assert (
+            _ADAPTER.translate_tool_choice_to_responses_api({"type": "auto"}) == "auto"
+        )
 
     def test_any_maps_to_required(self):
-        assert _ADAPTER.translate_tool_choice_to_responses_api({"type": "any"}) == {
-            "type": "required"
-        }
+        assert (
+            _ADAPTER.translate_tool_choice_to_responses_api({"type": "any"})
+            == "required"
+        )
+
+    def test_none_maps_to_none(self):
+        assert (
+            _ADAPTER.translate_tool_choice_to_responses_api({"type": "none"}) == "none"
+        )
 
     def test_specific_tool_maps_to_function(self):
         result = _ADAPTER.translate_tool_choice_to_responses_api(
@@ -603,8 +609,8 @@ class TestTranslateToolChoiceToResponsesAPI:
         assert result == {"type": "function", "name": "get_weather"}
 
     def test_unknown_type_defaults_to_auto(self):
-        result = _ADAPTER.translate_tool_choice_to_responses_api({"type": "none"})
-        assert result == {"type": "auto"}
+        result = _ADAPTER.translate_tool_choice_to_responses_api({"type": "auto"})
+        assert result == "auto"
 
 
 # ---------------------------------------------------------------------------