diff --git a/llama_stack/providers/utils/inference/openai_compat.py b/llama_stack/providers/utils/inference/openai_compat.py
index e51119b79..1a8d82de2 100644
--- a/llama_stack/providers/utils/inference/openai_compat.py
+++ b/llama_stack/providers/utils/inference/openai_compat.py
@@ -532,12 +532,17 @@ async def convert_message_to_openai_dict(message: Message, download: bool = Fals
     if hasattr(message, "tool_calls") and message.tool_calls:
         result["tool_calls"] = []
         for tc in message.tool_calls:
+            # The tool.tool_name can be a str or a BuiltinTool enum. If
+            # it's the latter, convert to a string.
+            tool_name = tc.tool_name
+            if isinstance(tool_name, BuiltinTool):
+                tool_name = tool_name.value
             result["tool_calls"].append(
                 {
                     "id": tc.call_id,
                     "type": "function",
                     "function": {
-                        "name": tc.tool_name,
+                        "name": tool_name,
                         "arguments": tc.arguments_json if hasattr(tc, "arguments_json") else json.dumps(tc.arguments),
                     },
                 }
diff --git a/tests/unit/providers/utils/inference/test_openai_compat.py b/tests/unit/providers/utils/inference/test_openai_compat.py
index eb02f8203..fda762d7f 100644
--- a/tests/unit/providers/utils/inference/test_openai_compat.py
+++ b/tests/unit/providers/utils/inference/test_openai_compat.py
@@ -8,7 +8,7 @@ import pytest
 
 from llama_stack.apis.common.content_types import TextContentItem
 from llama_stack.apis.inference.inference import CompletionMessage, UserMessage
-from llama_stack.models.llama.datatypes import StopReason, ToolCall
+from llama_stack.models.llama.datatypes import BuiltinTool, StopReason, ToolCall
 from llama_stack.providers.utils.inference.openai_compat import convert_message_to_openai_dict
 
 
@@ -41,3 +41,29 @@ async def test_convert_message_to_openai_dict_with_tool_call():
             {"id": "123", "type": "function", "function": {"name": "test_tool", "arguments": '{"foo": "bar"}'}}
         ],
     }
+
+
+@pytest.mark.asyncio
+async def test_convert_message_to_openai_dict_with_builtin_tool_call():
+    message = CompletionMessage(
+        content="",
+        tool_calls=[
+            ToolCall(
+                call_id="123",
+                tool_name=BuiltinTool.brave_search,
+                arguments_json='{"foo": "bar"}',
+                arguments={"foo": "bar"},
+            )
+        ],
+        stop_reason=StopReason.end_of_turn,
+    )
+
+    openai_dict = await convert_message_to_openai_dict(message)
+
+    assert openai_dict == {
+        "role": "assistant",
+        "content": [{"type": "text", "text": ""}],
+        "tool_calls": [
+            {"id": "123", "type": "function", "function": {"name": "brave_search", "arguments": '{"foo": "bar"}'}}
+        ],
+    }