fix(gemini): send googleMaps retrievalConfig in the request body

VertexGeminiConfig._map_function extracts latitude/longitude from a
googleMaps tool into optional_params["toolConfig"]["retrievalConfig"],
but _transform_request_body only built toolConfig from tool_choice, so
the location never reached Google and Maps grounding ran without it

Pop toolConfig from optional_params and merge it with tool_choice.
Type retrievalConfig on ToolConfig

litellm/llms/vertex_ai/gemini/transformation.py

@@ -1191,6 +1191,7 @@ def _transform_request_body(
             )
         tools: Final[Tools | None] = optional_params.pop("tools", None)
         tool_choice: Final[ToolConfig | None] = optional_params.pop("tool_choice", None)
+        tool_config: Final[ToolConfig | None] = optional_params.pop("toolConfig", None)
         include_server_side_tool_invocations: bool = optional_params.pop("include_server_side_tool_invocations", False)
         safety_settings: list[SafetSettingsConfig] | None = optional_params.pop("safety_settings", None)
         # Drop output_config as it's not supported by Vertex AI
@@ -1223,8 +1224,15 @@ def _transform_request_body(
                 data["system_instruction"] = system_instructions
             if tools is not None:
                 data["tools"] = tools
-            if tool_choice is not None:
-                data["toolConfig"] = tool_choice
+            merged_tool_config: Final[ToolConfig | None] = (
+                {**tool_config, **tool_choice}
+                if tool_config is not None and tool_choice is not None
+                else tool_config
+                if tool_config is not None
+                else tool_choice
+            )
+            if merged_tool_config is not None:
+                data["toolConfig"] = merged_tool_config
             if include_server_side_tool_invocations:
                 if "toolConfig" not in data:
                     data["toolConfig"] = {}

litellm/types/llms/vertex_ai.py

@@ -2,6 +2,7 @@ from enum import Enum
 from typing import Any, Final, Literal, Protocol
 
 from typing_extensions import (
+    ReadOnly,
     Required,
     TypedDict,
 )
@@ -278,9 +279,20 @@ class Tools(TypedDict, total=False):
     retrieval: Retrieval
 
 
+class LatLng(TypedDict):
+    latitude: ReadOnly[float]
+    longitude: ReadOnly[float]
+
+
+class RetrievalConfig(TypedDict, total=False):
+    latLng: ReadOnly[LatLng]
+    languageCode: ReadOnly[str]
+
+
 class ToolConfig(TypedDict, total=False):
     functionCallingConfig: FunctionCallingConfig
     includeServerSideToolInvocations: bool
+    retrievalConfig: ReadOnly[RetrievalConfig]
 
 
 class TTL(TypedDict, total=False):

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

@@ -338,3 +338,56 @@ def test_map_function_enterprise_web_search_snake_case():
 
     assert len(result) == 1
     assert "enterpriseWebSearch" in result[0]
+
+
+def test__transform_request_body_google_maps_retrieval_config_is_sent():
+    """
+    googleMaps latitude/longitude are extracted into optional_params["toolConfig"]["retrievalConfig"]
+    by VertexGeminiConfig._map_function. That toolConfig must reach the request body, otherwise
+    Google grounds without a location.
+    """
+    optional_params = {}
+    tools = VertexGeminiConfig()._map_function(
+        value=[{"googleMaps": {"latitude": 37.7749, "longitude": -122.4194}}],
+        optional_params=optional_params,
+    )
+    optional_params["tools"] = tools
+
+    rb: RequestBody = transformation._transform_request_body(
+        messages=[{"role": "user", "content": "coffee near me"}],
+        model="gemini-3-flash-preview",
+        optional_params=optional_params,
+        custom_llm_provider="gemini",
+        litellm_params={},
+        cached_content=None,
+    )
+
+    assert rb["tools"] == [{"googleMaps": {}}]
+    assert rb["toolConfig"] == {"retrievalConfig": {"latLng": {"latitude": 37.7749, "longitude": -122.4194}}}
+
+
+def test__transform_request_body_tool_config_merges_with_tool_choice():
+    """
+    A googleMaps retrievalConfig and a function-calling tool_choice both live under toolConfig;
+    neither should clobber the other.
+    """
+    optional_params = {
+        "toolConfig": {"retrievalConfig": {"latLng": {"latitude": 1.0, "longitude": 2.0}}},
+        "tool_choice": {"functionCallingConfig": {"mode": "AUTO"}},
+        "include_server_side_tool_invocations": True,
+    }
+
+    rb: RequestBody = transformation._transform_request_body(
+        messages=[{"role": "user", "content": "hi"}],
+        model="gemini-3-flash-preview",
+        optional_params=optional_params,
+        custom_llm_provider="gemini",
+        litellm_params={},
+        cached_content=None,
+    )
+
+    assert rb["toolConfig"] == {
+        "retrievalConfig": {"latLng": {"latitude": 1.0, "longitude": 2.0}},
+        "functionCallingConfig": {"mode": "AUTO"},
+        "includeServerSideToolInvocations": True,
+    }