diff --git a/src/google/adk/tools/retrieval/vertex_ai_rag_retrieval.py b/src/google/adk/tools/retrieval/vertex_ai_rag_retrieval.py
index b0acc0feb8..7d7dbf8f06 100644
--- a/src/google/adk/tools/retrieval/vertex_ai_rag_retrieval.py
+++ b/src/google/adk/tools/retrieval/vertex_ai_rag_retrieval.py
@@ -23,7 +23,6 @@
 from google.genai import types
 from typing_extensions import override
 
-from ...utils.model_name_utils import is_gemini_2_or_above
 from ..tool_context import ToolContext
 from .base_retrieval_tool import BaseRetrievalTool
 
@@ -62,26 +61,10 @@ async def process_llm_request(
       tool_context: ToolContext,
       llm_request: LlmRequest,
   ) -> None:
-    # Use Gemini built-in Vertex AI RAG tool for Gemini 2 models.
-    if is_gemini_2_or_above(llm_request.model):
-      llm_request.config = (
-          types.GenerateContentConfig()
-          if not llm_request.config
-          else llm_request.config
-      )
-      llm_request.config.tools = (
-          [] if not llm_request.config.tools else llm_request.config.tools
-      )
-      llm_request.config.tools.append(
-          types.Tool(
-              retrieval=types.Retrieval(vertex_rag_store=self.vertex_rag_store)
-          )
-      )
-    else:
-      # Add the function declaration to the tools
-      await super().process_llm_request(
-          tool_context=tool_context, llm_request=llm_request
-      )
+    # Add the function declaration to the tools
+    await super().process_llm_request(
+        tool_context=tool_context, llm_request=llm_request
+    )
 
   @override
   async def run_async(
diff --git a/tests/unittests/tools/retrieval/test_vertex_ai_rag_retrieval.py b/tests/unittests/tools/retrieval/test_vertex_ai_rag_retrieval.py
index 132e6b7b10..333b267718 100644
--- a/tests/unittests/tools/retrieval/test_vertex_ai_rag_retrieval.py
+++ b/tests/unittests/tools/retrieval/test_vertex_ai_rag_retrieval.py
@@ -133,15 +133,8 @@ def test_vertex_rag_retrieval_for_gemini_2_x():
       ('user', 'test1'),
   ]
   assert len(mockModel.requests[0].config.tools) == 1
-  assert mockModel.requests[0].config.tools == [
-      types.Tool(
-          retrieval=types.Retrieval(
-              vertex_rag_store=types.VertexRagStore(
-                  rag_corpora=[
-                      'projects/123456789/locations/us-central1/ragCorpora/1234567890'
-                  ]
-              )
-          )
-      )
-  ]
-  assert 'rag_retrieval' not in mockModel.requests[0].tools_dict
+  assert (
+      mockModel.requests[0].config.tools[0].function_declarations[0].name
+      == 'rag_retrieval'
+  )
+  assert mockModel.requests[0].tools_dict['rag_retrieval'] is not None