diff --git a/litellm/tests/test_amazing_vertex_completion.py b/litellm/tests/test_amazing_vertex_completion.py
index ce9e6286f..c58541a7d 100644
--- a/litellm/tests/test_amazing_vertex_completion.py
+++ b/litellm/tests/test_amazing_vertex_completion.py
@@ -638,73 +638,66 @@ async def test_gemini_pro_function_calling(sync_mode):
 # gemini_pro_function_calling()
 
 
-@pytest.mark.parametrize("stream", [False, True])
 @pytest.mark.parametrize("sync_mode", [False, True])
 @pytest.mark.asyncio
-async def test_gemini_pro_function_calling_streaming(stream, sync_mode):
+async def test_gemini_pro_function_calling_streaming(sync_mode):
     load_vertex_ai_credentials()
     litellm.set_verbose = True
-    tools = [
-        {
-            "type": "function",
-            "function": {
-                "name": "get_current_weather",
-                "description": "Get the current weather in a given location",
-                "parameters": {
-                    "type": "object",
-                    "properties": {
-                        "location": {
-                            "type": "string",
-                            "description": "The city and state, e.g. San Francisco, CA",
+    data = {
+        "model": "vertex_ai/gemini-pro",
+        "messages": [
+            {
+                "role": "user",
+                "content": "Call the submit_cities function with San Francisco and New York",
+            }
+        ],
+        "tools": [
+            {
+                "type": "function",
+                "function": {
+                    "name": "submit_cities",
+                    "description": "Submits a list of cities",
+                    "parameters": {
+                        "type": "object",
+                        "properties": {
+                            "cities": {"type": "array", "items": {"type": "string"}}
                         },
-                        "unit": {"type": "string", "enum": ["celsius", "fahrenheit"]},
+                        "required": ["cities"],
                     },
-                    "required": ["location"],
                 },
-            },
-        }
-    ]
-    messages = [
-        {
-            "role": "user",
-            "content": "What's the weather like in Boston today in fahrenheit?",
-        }
-    ]
-    optional_params = {
-        "tools": tools,
+            }
+        ],
         "tool_choice": "auto",
         "n": 1,
-        "stream": stream,
+        "stream": True,
         "temperature": 0.1,
     }
+    chunks = []
     try:
         if sync_mode == True:
-            response = litellm.completion(
-                model="gemini-pro", messages=messages, **optional_params
-            )
+            response = litellm.completion(**data)
             print(f"completion: {response}")
 
-            if stream == True:
-                # assert completion.choices[0].message.content is None
-                # assert len(completion.choices[0].message.tool_calls) == 1
-                for chunk in response:
-                    assert isinstance(chunk, litellm.ModelResponse)
-            else:
-                assert isinstance(response, litellm.ModelResponse)
+            for chunk in response:
+                chunks.append(chunk)
+                assert isinstance(chunk, litellm.ModelResponse)
         else:
-            response = await litellm.acompletion(
-                model="gemini-pro", messages=messages, **optional_params
-            )
+            response = await litellm.acompletion(**data)
             print(f"completion: {response}")
 
-            if stream == True:
-                # assert completion.choices[0].message.content is None
-                # assert len(completion.choices[0].message.tool_calls) == 1
-                async for chunk in response:
-                    print(f"chunk: {chunk}")
-                    assert isinstance(chunk, litellm.ModelResponse)
-            else:
-                assert isinstance(response, litellm.ModelResponse)
+            assert isinstance(response, litellm.CustomStreamWrapper)
+
+            async for chunk in response:
+                print(f"chunk: {chunk}")
+                chunks.append(chunk)
+                assert isinstance(chunk, litellm.ModelResponse)
+
+        complete_response = litellm.stream_chunk_builder(chunks=chunks)
+        assert (
+            complete_response.choices[0].message.content is not None
+            or len(complete_response.choices[0].message.tool_calls) > 0
+        )
+        print(f"complete_response: {complete_response}")
     except litellm.APIError as e:
         pass
     except litellm.RateLimitError as e:
diff --git a/litellm/utils.py b/litellm/utils.py
index f77baf8bd..cd21b390b 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -10761,6 +10761,8 @@ class CustomStreamWrapper:
                 else:
                     completion_obj["content"] = str(chunk)
             elif self.custom_llm_provider and (self.custom_llm_provider == "vertex_ai"):
+                import proto  # type: ignore
+
                 if self.model.startswith("claude-3"):
                     response_obj = self.handle_vertexai_anthropic_chunk(chunk=chunk)
                     if response_obj is None:
@@ -10798,10 +10800,24 @@ class CustomStreamWrapper:
                                 function_call = (
                                     chunk.candidates[0].content.parts[0].function_call
                                 )
+
                                 args_dict = {}
-                                for k, v in function_call.args.items():
-                                    args_dict[k] = v
-                                args_str = json.dumps(args_dict)
+
+                                # Check if it's a RepeatedComposite instance
+                                for key, val in function_call.args.items():
+                                    if isinstance(
+                                        val,
+                                        proto.marshal.collections.repeated.RepeatedComposite,
+                                    ):
+                                        # If so, convert to list
+                                        args_dict[key] = [v for v in val]
+                                    else:
+                                        args_dict[key] = val
+
+                                try:
+                                    args_str = json.dumps(args_dict)
+                                except Exception as e:
+                                    raise e
                                 _delta_obj = litellm.utils.Delta(
                                     content=None,
                                     tool_calls=[