diff --git a/contributing/samples/langchain_structured_tool_agent/agent.py b/contributing/samples/langchain_structured_tool_agent/agent.py
index 5c4c5b9a2..fc0d51d54 100644
--- a/contributing/samples/langchain_structured_tool_agent/agent.py
+++ b/contributing/samples/langchain_structured_tool_agent/agent.py
@@ -15,6 +15,8 @@
 """
 This agent aims to test the Langchain tool with Langchain's StructuredTool
 """
+from __future__ import annotations
+
 from google.adk.agents.llm_agent import Agent
 from google.adk.tools.langchain_tool import LangchainTool
 from langchain.tools import tool
@@ -23,11 +25,13 @@
 
 
 async def add(x, y) -> int:
+  """Adds two numbers."""
   return x + y
 
 
 @tool
 def minus(x, y) -> int:
+  """Minus two numbers."""
   return x - y
 
 
diff --git a/src/google/adk/agents/llm_agent.py b/src/google/adk/agents/llm_agent.py
index ae55dd1e4..ba2614f20 100644
--- a/src/google/adk/agents/llm_agent.py
+++ b/src/google/adk/agents/llm_agent.py
@@ -109,7 +109,8 @@
 
 
 async def _convert_tool_union_to_tools(
-    tool_union: ToolUnion, ctx: ReadonlyContext
+    tool_union: ToolUnion,
+    ctx: ReadonlyContext,
 ) -> list[BaseTool]:
   if isinstance(tool_union, BaseTool):
     return [tool_union]
diff --git a/src/google/adk/flows/llm_flows/base_llm_flow.py b/src/google/adk/flows/llm_flows/base_llm_flow.py
index 90cf0fbcf..16a7322f1 100644
--- a/src/google/adk/flows/llm_flows/base_llm_flow.py
+++ b/src/google/adk/flows/llm_flows/base_llm_flow.py
@@ -73,7 +73,7 @@ async def run_live(
       invocation_context: InvocationContext,
   ) -> AsyncGenerator[Event, None]:
     """Runs the flow using live api."""
-    llm_request = LlmRequest()
+    llm_request = LlmRequest(live_connect_config=types.LiveConnectConfig())
     event_id = Event.new_id()
 
     # Preprocess before calling the LLM.
@@ -373,7 +373,9 @@ async def _run_one_step_async(
         yield event
 
   async def _preprocess_async(
-      self, invocation_context: InvocationContext, llm_request: LlmRequest
+      self,
+      invocation_context: InvocationContext,
+      llm_request: LlmRequest,
   ) -> AsyncGenerator[Event, None]:
     from ...agents.llm_agent import LlmAgent
 
diff --git a/src/google/adk/flows/llm_flows/basic.py b/src/google/adk/flows/llm_flows/basic.py
index 549c6d875..e5b4fd627 100644
--- a/src/google/adk/flows/llm_flows/basic.py
+++ b/src/google/adk/flows/llm_flows/basic.py
@@ -57,30 +57,31 @@ async def run_async(
     if agent.output_schema and not agent.tools:
       llm_request.set_output_schema(agent.output_schema)
 
-    llm_request.live_connect_config.response_modalities = (
-        invocation_context.run_config.response_modalities
-    )
-    llm_request.live_connect_config.speech_config = (
-        invocation_context.run_config.speech_config
-    )
-    llm_request.live_connect_config.output_audio_transcription = (
-        invocation_context.run_config.output_audio_transcription
-    )
-    llm_request.live_connect_config.input_audio_transcription = (
-        invocation_context.run_config.input_audio_transcription
-    )
-    llm_request.live_connect_config.realtime_input_config = (
-        invocation_context.run_config.realtime_input_config
-    )
-    llm_request.live_connect_config.enable_affective_dialog = (
-        invocation_context.run_config.enable_affective_dialog
-    )
-    llm_request.live_connect_config.proactivity = (
-        invocation_context.run_config.proactivity
-    )
-    llm_request.live_connect_config.session_resumption = (
-        invocation_context.run_config.session_resumption
-    )
+    if llm_request.live_connect_config:
+      llm_request.live_connect_config.response_modalities = (
+          invocation_context.run_config.response_modalities
+      )
+      llm_request.live_connect_config.speech_config = (
+          invocation_context.run_config.speech_config
+      )
+      llm_request.live_connect_config.output_audio_transcription = (
+          invocation_context.run_config.output_audio_transcription
+      )
+      llm_request.live_connect_config.input_audio_transcription = (
+          invocation_context.run_config.input_audio_transcription
+      )
+      llm_request.live_connect_config.realtime_input_config = (
+          invocation_context.run_config.realtime_input_config
+      )
+      llm_request.live_connect_config.enable_affective_dialog = (
+          invocation_context.run_config.enable_affective_dialog
+      )
+      llm_request.live_connect_config.proactivity = (
+          invocation_context.run_config.proactivity
+      )
+      llm_request.live_connect_config.session_resumption = (
+          invocation_context.run_config.session_resumption
+      )
 
     # TODO: handle tool append here, instead of in BaseTool.process_llm_request.
 
diff --git a/src/google/adk/models/llm_request.py b/src/google/adk/models/llm_request.py
index b83fd1d99..86d1d17e1 100644
--- a/src/google/adk/models/llm_request.py
+++ b/src/google/adk/models/llm_request.py
@@ -14,6 +14,9 @@
 
 from __future__ import annotations
 
+from collections.abc import AsyncGenerator as ABCAsyncGenerator
+import inspect
+from typing import get_origin
 from typing import Optional
 
 from google.genai import types
@@ -22,6 +25,7 @@
 from pydantic import Field
 
 from ..tools.base_tool import BaseTool
+from ..tools.function_tool import FunctionTool
 
 
 def _find_tool_with_function_declarations(
@@ -66,13 +70,13 @@ class LlmRequest(BaseModel):
   config: types.GenerateContentConfig = Field(
       default_factory=types.GenerateContentConfig
   )
-  live_connect_config: types.LiveConnectConfig = Field(
-      default_factory=types.LiveConnectConfig
-  )
   """Additional config for the generate content request.
 
   tools in generate_content_config should not be set.
   """
+  live_connect_config: Optional[types.LiveConnectConfig] = None
+  """Live connection config.
+  """
   tools_dict: dict[str, BaseTool] = Field(default_factory=dict, exclude=True)
   """The tools dictionary."""
 
@@ -99,7 +103,23 @@ def append_tools(self, tools: list[BaseTool]) -> None:
       return
     declarations = []
     for tool in tools:
-      declaration = tool._get_declaration()
+      if self.live_connect_config is not None:
+        # ignore response for tools that returns AsyncGenerator that the model
+        # can't understand yet even though the model can't handle it, streaming
+        # tools can handle it.
+        # to check type, use typing.collections.abc.AsyncGenerator and not
+        # typing.AsyncGenerator
+        is_async_generator_return = False
+        if isinstance(tool, FunctionTool):
+          signature = inspect.signature(tool.func)
+          is_async_generator_return = (
+              get_origin(signature.return_annotation) is ABCAsyncGenerator
+          )
+        declaration = tool._get_declaration(
+            ignore_return_declaration=is_async_generator_return
+        )
+      else:
+        declaration = tool._get_declaration()
       if declaration:
         declarations.append(declaration)
         self.tools_dict[tool.name] = tool
diff --git a/src/google/adk/tools/_automatic_function_calling_util.py b/src/google/adk/tools/_automatic_function_calling_util.py
index 5e32f68e0..1a89442f3 100644
--- a/src/google/adk/tools/_automatic_function_calling_util.py
+++ b/src/google/adk/tools/_automatic_function_calling_util.py
@@ -195,6 +195,7 @@ def build_function_declaration(
     func: Union[Callable, BaseModel],
     ignore_params: Optional[list[str]] = None,
     variant: GoogleLLMVariant = GoogleLLMVariant.GEMINI_API,
+    ignore_return_declaration: bool = False,
 ) -> types.FunctionDeclaration:
   signature = inspect.signature(func)
   should_update_signature = False
@@ -232,9 +233,11 @@ def build_function_declaration(
       new_func.__annotations__ = func.__annotations__
 
   return (
-      from_function_with_options(func, variant)
+      from_function_with_options(func, variant, ignore_return_declaration)
       if not should_update_signature
-      else from_function_with_options(new_func, variant)
+      else from_function_with_options(
+          new_func, variant, ignore_return_declaration
+      )
   )
 
 
@@ -293,6 +296,7 @@ def build_function_declaration_util(
 def from_function_with_options(
     func: Callable,
     variant: GoogleLLMVariant = GoogleLLMVariant.GEMINI_API,
+    ignore_return_declaration: bool = False,
 ) -> 'types.FunctionDeclaration':
 
   parameters_properties = {}
@@ -324,7 +328,8 @@ def from_function_with_options(
             declaration.parameters
         )
     )
-  if variant == GoogleLLMVariant.GEMINI_API:
+
+  if variant == GoogleLLMVariant.GEMINI_API or ignore_return_declaration:
     return declaration
 
   return_annotation = inspect.signature(func).return_annotation
diff --git a/src/google/adk/tools/agent_tool.py b/src/google/adk/tools/agent_tool.py
index c0d07238d..abe0d13d9 100644
--- a/src/google/adk/tools/agent_tool.py
+++ b/src/google/adk/tools/agent_tool.py
@@ -15,6 +15,7 @@
 from __future__ import annotations
 
 from typing import Any
+from typing import Optional
 from typing import TYPE_CHECKING
 
 from google.genai import types
@@ -61,7 +62,9 @@ def populate_name(cls, data: Any) -> Any:
     return data
 
   @override
-  def _get_declaration(self) -> types.FunctionDeclaration:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     from ..agents.llm_agent import LlmAgent
     from ..utils.variant_utils import GoogleLLMVariant
 
diff --git a/src/google/adk/tools/application_integration_tool/integration_connector_tool.py b/src/google/adk/tools/application_integration_tool/integration_connector_tool.py
index 0f1a6895d..7c3e27499 100644
--- a/src/google/adk/tools/application_integration_tool/integration_connector_tool.py
+++ b/src/google/adk/tools/application_integration_tool/integration_connector_tool.py
@@ -20,7 +20,7 @@
 from typing import Optional
 from typing import Union
 
-from google.genai.types import FunctionDeclaration
+from google.genai import types
 from typing_extensions import override
 
 from ...auth.auth_credential import AuthCredential
@@ -115,7 +115,9 @@ def __init__(
     self._auth_credential = auth_credential
 
   @override
-  def _get_declaration(self) -> FunctionDeclaration:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     """Returns the function declaration in the Gemini Schema format."""
     schema_dict = self._rest_api_tool._operation_parser.get_json_schema()
     for field in self.EXCLUDE_FIELDS:
@@ -126,7 +128,7 @@ def _get_declaration(self) -> FunctionDeclaration:
         schema_dict['required'].remove(field)
 
     parameters = _to_gemini_schema(schema_dict)
-    function_decl = FunctionDeclaration(
+    function_decl = types.FunctionDeclaration(
         name=self.name, description=self.description, parameters=parameters
     )
     return function_decl
diff --git a/src/google/adk/tools/base_tool.py b/src/google/adk/tools/base_tool.py
index 90c575395..eb91adcd6 100644
--- a/src/google/adk/tools/base_tool.py
+++ b/src/google/adk/tools/base_tool.py
@@ -78,7 +78,9 @@ def __init__(
     self.is_long_running = is_long_running
     self.custom_metadata = custom_metadata
 
-  def _get_declaration(self) -> Optional[types.FunctionDeclaration]:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     """Gets the OpenAPI specification of this tool in the form of a FunctionDeclaration.
 
     NOTE:
diff --git a/src/google/adk/tools/crewai_tool.py b/src/google/adk/tools/crewai_tool.py
index 9dfe7cc75..7af00fe74 100644
--- a/src/google/adk/tools/crewai_tool.py
+++ b/src/google/adk/tools/crewai_tool.py
@@ -14,6 +14,8 @@
 
 from __future__ import annotations
 
+from typing import Optional
+
 from google.genai import types
 from typing_extensions import override
 
@@ -62,7 +64,9 @@ def __init__(self, tool: CrewaiBaseTool, *, name: str, description: str):
       self.description = tool.description
 
   @override
-  def _get_declaration(self) -> types.FunctionDeclaration:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     """Build the function declaration for the tool."""
     function_declaration = _automatic_function_calling_util.build_function_declaration_for_params_for_crewai(
         False,
diff --git a/src/google/adk/tools/function_tool.py b/src/google/adk/tools/function_tool.py
index 2687f1200..564cd3100 100644
--- a/src/google/adk/tools/function_tool.py
+++ b/src/google/adk/tools/function_tool.py
@@ -62,7 +62,9 @@ def __init__(self, func: Callable[..., Any]):
     self._ignore_params = ['tool_context', 'input_stream']
 
   @override
-  def _get_declaration(self) -> Optional[types.FunctionDeclaration]:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     function_decl = types.FunctionDeclaration.model_validate(
         build_function_declaration(
             func=self.func,
@@ -70,6 +72,7 @@ def _get_declaration(self) -> Optional[types.FunctionDeclaration]:
             # input_stream is for streaming tool
             ignore_params=self._ignore_params,
             variant=self._api_variant,
+            ignore_return_declaration=ignore_return_declaration,
         )
     )
 
diff --git a/src/google/adk/tools/google_api_tool/google_api_tool.py b/src/google/adk/tools/google_api_tool/google_api_tool.py
index d2bac5686..645822da1 100644
--- a/src/google/adk/tools/google_api_tool/google_api_tool.py
+++ b/src/google/adk/tools/google_api_tool/google_api_tool.py
@@ -11,14 +11,13 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
 from __future__ import annotations
 
 from typing import Any
 from typing import Dict
 from typing import Optional
 
-from google.genai.types import FunctionDeclaration
+from google.genai import types
 from typing_extensions import override
 
 from ...auth.auth_credential import AuthCredential
@@ -52,7 +51,9 @@ def __init__(
       self.configure_auth(client_id, client_secret)
 
   @override
-  def _get_declaration(self) -> FunctionDeclaration:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     return self._rest_api_tool._get_declaration()
 
   @override
diff --git a/src/google/adk/tools/langchain_tool.py b/src/google/adk/tools/langchain_tool.py
index 44f884ff6..06cea4971 100644
--- a/src/google/adk/tools/langchain_tool.py
+++ b/src/google/adk/tools/langchain_tool.py
@@ -101,7 +101,9 @@ def __init__(
     # else: keep default from FunctionTool
 
   @override
-  def _get_declaration(self) -> types.FunctionDeclaration:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     """Build the function declaration for the tool.
 
     Returns:
diff --git a/src/google/adk/tools/load_artifacts_tool.py b/src/google/adk/tools/load_artifacts_tool.py
index db28aefb9..e5d419a09 100644
--- a/src/google/adk/tools/load_artifacts_tool.py
+++ b/src/google/adk/tools/load_artifacts_tool.py
@@ -16,6 +16,7 @@
 
 import json
 from typing import Any
+from typing import Optional
 from typing import TYPE_CHECKING
 
 from google.genai import types
@@ -37,7 +38,10 @@ def __init__(self):
         description='Loads the artifacts and adds them to the session.',
     )
 
-  def _get_declaration(self) -> types.FunctionDeclaration | None:
+  @override
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     return types.FunctionDeclaration(
         name=self.name,
         description=self.description,
diff --git a/src/google/adk/tools/load_memory_tool.py b/src/google/adk/tools/load_memory_tool.py
index 8410e4114..02cb82d41 100644
--- a/src/google/adk/tools/load_memory_tool.py
+++ b/src/google/adk/tools/load_memory_tool.py
@@ -14,6 +14,7 @@
 
 from __future__ import annotations
 
+from typing import Optional
 from typing import TYPE_CHECKING
 
 from google.genai import types
@@ -58,7 +59,9 @@ def __init__(self):
     super().__init__(load_memory)
 
   @override
-  def _get_declaration(self) -> types.FunctionDeclaration | None:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     return types.FunctionDeclaration(
         name=self.name,
         description=self.description,
diff --git a/src/google/adk/tools/long_running_tool.py b/src/google/adk/tools/long_running_tool.py
index 628d01324..e70884ee5 100644
--- a/src/google/adk/tools/long_running_tool.py
+++ b/src/google/adk/tools/long_running_tool.py
@@ -45,7 +45,9 @@ def __init__(self, func: Callable):
     self.is_long_running = True
 
   @override
-  def _get_declaration(self) -> Optional[types.FunctionDeclaration]:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     declaration = super()._get_declaration()
     if declaration:
       instruction = (
diff --git a/src/google/adk/tools/mcp_tool/mcp_tool.py b/src/google/adk/tools/mcp_tool/mcp_tool.py
index af4616cae..42ae66e4d 100644
--- a/src/google/adk/tools/mcp_tool/mcp_tool.py
+++ b/src/google/adk/tools/mcp_tool/mcp_tool.py
@@ -19,6 +19,7 @@
 from typing import Optional
 
 from fastapi.openapi.models import APIKeyIn
+from google.genai import types
 from google.genai.types import FunctionDeclaration
 from typing_extensions import override
 
@@ -97,7 +98,9 @@ def __init__(
     self._mcp_session_manager = mcp_session_manager
 
   @override
-  def _get_declaration(self) -> FunctionDeclaration:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     """Gets the function declaration for the tool.
 
     Returns:
diff --git a/src/google/adk/tools/openapi_tool/openapi_spec_parser/rest_api_tool.py b/src/google/adk/tools/openapi_tool/openapi_spec_parser/rest_api_tool.py
index 0df9461b9..2323f3ffa 100644
--- a/src/google/adk/tools/openapi_tool/openapi_spec_parser/rest_api_tool.py
+++ b/src/google/adk/tools/openapi_tool/openapi_spec_parser/rest_api_tool.py
@@ -23,6 +23,7 @@
 from typing import Union
 
 from fastapi.openapi.models import Operation
+from google.genai import types
 from google.genai.types import FunctionDeclaration
 import requests
 from typing_extensions import override
@@ -181,7 +182,9 @@ def from_parsed_operation_str(
     return RestApiTool.from_parsed_operation(operation)
 
   @override
-  def _get_declaration(self) -> FunctionDeclaration:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     """Returns the function declaration in the Gemini Schema format."""
     schema_dict = self._operation_parser.get_json_schema()
     parameters = _to_gemini_schema(schema_dict)
diff --git a/src/google/adk/tools/retrieval/base_retrieval_tool.py b/src/google/adk/tools/retrieval/base_retrieval_tool.py
index 64f3ec91d..40c6c991a 100644
--- a/src/google/adk/tools/retrieval/base_retrieval_tool.py
+++ b/src/google/adk/tools/retrieval/base_retrieval_tool.py
@@ -11,6 +11,9 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from __future__ import annotations
+
+from typing import Optional
 
 from google.genai import types
 from typing_extensions import override
@@ -21,7 +24,9 @@
 class BaseRetrievalTool(BaseTool):
 
   @override
-  def _get_declaration(self) -> types.FunctionDeclaration:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     return types.FunctionDeclaration(
         name=self.name,
         description=self.description,
diff --git a/src/google/adk/tools/set_model_response_tool.py b/src/google/adk/tools/set_model_response_tool.py
index 6b27d55c2..da8fd1536 100644
--- a/src/google/adk/tools/set_model_response_tool.py
+++ b/src/google/adk/tools/set_model_response_tool.py
@@ -81,7 +81,9 @@ def set_model_response() -> str:
     )
 
   @override
-  def _get_declaration(self) -> Optional[types.FunctionDeclaration]:
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     """Gets the OpenAPI specification of this tool."""
     function_decl = types.FunctionDeclaration.model_validate(
         build_function_declaration(
diff --git a/tests/unittests/models/test_llm_request.py b/tests/unittests/models/test_llm_request.py
index 789422968..8fcd877ad 100644
--- a/tests/unittests/models/test_llm_request.py
+++ b/tests/unittests/models/test_llm_request.py
@@ -26,6 +26,7 @@
 from google.adk.tools.tool_context import ToolContext
 from google.genai import types
 import pytest
+from typing_extensions import override
 
 
 def dummy_tool(query: str) -> str:
@@ -178,7 +179,10 @@ class _MockTool(BaseTool):
   def __init__(self, name: str):
     super().__init__(name=name, description=f'Mock tool {name}')
 
-  def _get_declaration(self) -> Optional[types.FunctionDeclaration]:
+  @override
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     return types.FunctionDeclaration(
         name=self.name,
         description=self.description,
diff --git a/tests/unittests/tools/test_base_tool.py b/tests/unittests/tools/test_base_tool.py
index da1dda64d..4264b1d04 100644
--- a/tests/unittests/tools/test_base_tool.py
+++ b/tests/unittests/tools/test_base_tool.py
@@ -22,6 +22,7 @@
 from google.adk.tools.tool_context import ToolContext
 from google.genai import types
 import pytest
+from typing_extensions import override
 
 
 class _TestingTool(BaseTool):
@@ -33,7 +34,10 @@ def __init__(
     super().__init__(name='test_tool', description='test_description')
     self.declaration = declaration
 
-  def _get_declaration(self) -> Optional[types.FunctionDeclaration]:
+  @override
+  def _get_declaration(
+      self, ignore_return_declaration: bool = False
+  ) -> Optional[types.FunctionDeclaration]:
     return self.declaration