fix(vertex): drop mixed search tools with functions

litellm/llms/vertex_ai/gemini/vertex_and_google_ai_studio_gemini.py

@@ -1223,6 +1223,38 @@ class VertexGeminiConfig(VertexAIBaseConfig, BaseConfig):
             if "temperature" not in optional_params:
                 optional_params["temperature"] = 1.0
 
+        # web_search_options can be added before function tools are mapped, so
+        # strip any pre-existing search tools here as well to keep the request
+        # valid regardless of parameter order.
+        tools = optional_params.get("tools")
+        if (
+            isinstance(tools, list)
+            and any("function_declarations" in tool for tool in tools)
+            and not optional_params.get("include_server_side_tool_invocations", False)
+        ):
+            filtered_tools = [
+                tool
+                for tool in tools
+                if not any(
+                    search_tool in tool
+                    for search_tool in [
+                        VertexToolName.GOOGLE_SEARCH.value,
+                        VertexToolName.GOOGLE_SEARCH_RETRIEVAL.value,
+                        VertexToolName.ENTERPRISE_WEB_SEARCH.value,
+                        VertexToolName.URL_CONTEXT.value,
+                    ]
+                )
+            ]
+            if len(filtered_tools) != len(tools):
+                verbose_logger.warning(
+                    "Vertex AI does not support mixing function declarations with "
+                    "search tools (googleSearch, enterpriseWebSearch, urlContext, "
+                    "googleSearchRetrieval) in the same request. Dropping search "
+                    "tools and keeping function declarations. To use search tools, "
+                    "send a request without function calling tools."
+                )
+                optional_params["tools"] = filtered_tools
+
         return optional_params
 
     def get_mapped_special_auth_params(self) -> dict:

tests/test_litellm/llms/vertex_ai/gemini/test_vertex_web_search_tool_order.py

@@ -0,0 +1,35 @@
+def test_vertex_ai_web_search_options_dropped_when_function_tools_are_present():
+    """Test that search tools are dropped even when web_search_options is mapped first."""
+    from litellm.llms.vertex_ai.gemini.vertex_and_google_ai_studio_gemini import (
+        VertexGeminiConfig,
+    )
+
+    v = VertexGeminiConfig()
+
+    non_default_params = {
+        "web_search_options": {},
+        "tools": [
+            {
+                "type": "function",
+                "function": {
+                    "name": "notion_search",
+                    "description": "Search Notion",
+                    "parameters": {
+                        "type": "object",
+                        "properties": {"query": {"type": "string"}},
+                    },
+                },
+            }
+        ],
+    }
+
+    result = v.map_openai_params(
+        non_default_params=non_default_params,
+        optional_params={},
+        model="gemini-2.5-pro",
+        drop_params=True,
+    )
+
+    assert len(result["tools"]) == 1
+    assert "function_declarations" in result["tools"][0]
+    assert "googleSearch" not in result["tools"][0]