diff --git a/litellm/proxy/guardrails/guardrail_hooks/tool_permission.py b/litellm/proxy/guardrails/guardrail_hooks/tool_permission.py
index 74065522761..3cc46690b57 100644
--- a/litellm/proxy/guardrails/guardrail_hooks/tool_permission.py
+++ b/litellm/proxy/guardrails/guardrail_hooks/tool_permission.py
@@ -620,12 +620,10 @@ class ToolPermissionGuardrail(CustomGuardrail):
             return None
         if isinstance(tool_choice, str):
             return tool_choice
-        choice_type: Final[object] = self._get_mapping_value(tool_choice, "type")
-        if choice_type == "tool":
-            return self._get_mapping_value(tool_choice, "name")
-        if choice_type != "function":
+        if self._get_mapping_value(tool_choice, "type") not in ("tool", "function"):
             return None
-        return self._get_mapping_value(self._get_mapping_value(tool_choice, "function"), "name")
+        function_name: Final = self._get_mapping_value(self._get_mapping_value(tool_choice, "function"), "name")
+        return function_name or self._get_mapping_value(tool_choice, "name")
 
     @staticmethod
     def _is_anthropic_tool_choice(data: Mapping[str, object]) -> bool:
diff --git a/tests/test_litellm/proxy/guardrails/guardrail_hooks/test_tool_permission.py b/tests/test_litellm/proxy/guardrails/guardrail_hooks/test_tool_permission.py
index 7e8b89c8833..bc43f35ef47 100644
--- a/tests/test_litellm/proxy/guardrails/guardrail_hooks/test_tool_permission.py
+++ b/tests/test_litellm/proxy/guardrails/guardrail_hooks/test_tool_permission.py
@@ -1203,15 +1203,32 @@ class TestToolPermissionGuardrailAnthropicMessages:
         assert excinfo.value.detail["detection_message"] == "Tool 'Read' denied by rule 'deny_read'"
 
     @pytest.mark.asyncio
-    async def test_pre_call_rewrite_strips_denied_anthropic_tool_and_forced_choice(self):
+    @pytest.mark.parametrize(
+        ("tool_shape", "tool_choice", "call_type", "expected_tool_choice"),
+        [
+            (
+                {"input_schema": {"type": "object", "properties": {}}},
+                {"type": "tool", "name": "Read"},
+                "anthropic_messages",
+                {"type": "none"},
+            ),
+            (
+                {"type": "function", "parameters": {"type": "object", "properties": {}}},
+                {"type": "function", "name": "Read"},
+                "responses",
+                "none",
+            ),
+        ],
+        ids=["anthropic", "responses_api"],
+    )
+    async def test_pre_call_rewrite_strips_denied_flat_tool_and_forced_choice(
+        self, tool_shape, tool_choice, call_type, expected_tool_choice
+    ):
         data = {
             "model": "claude-sonnet-4-5",
             "messages": [{"role": "user", "content": "hi"}],
-            "tools": [
-                {"name": "Bash", "input_schema": {"type": "object", "properties": {}}},
-                {"name": "Read", "input_schema": {"type": "object", "properties": {}}},
-            ],
-            "tool_choice": {"type": "tool", "name": "Read"},
+            "tools": [{"name": "Bash", **tool_shape}, {"name": "Read", **tool_shape}],
+            "tool_choice": tool_choice,
         }
 
         with patch.object(self.rewriting, "should_run_guardrail", return_value=True):
@@ -1219,11 +1236,11 @@ class TestToolPermissionGuardrailAnthropicMessages:
                 user_api_key_dict=UserAPIKeyAuth(),
                 cache=DualCache(default_in_memory_ttl=1),
                 data=data,
-                call_type="anthropic_messages",
+                call_type=call_type,
             )
 
         assert [tool["name"] for tool in result["tools"]] == ["Bash"]
-        assert result["tool_choice"] == {"type": "none"}
+        assert result["tool_choice"] == expected_tool_choice
 
     @pytest.mark.asyncio
     async def test_denied_anthropic_tool_use_is_blocked(self):