Error in using Multiple MCP server tools in different ADK agents (code implementation)

[Karthik-Manne]

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• SDK Usage
• Server Implementation
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Your Question

I am working on creating a multi agent system using google ADK agents and MCP servers for tools.
I have a sample code with two agents and each agent using tools from different MCP servers.

Here is the code I have, implementing the multi agent system.

`from google.adk.agents.llm_agent import LlmAgent
from google.adk.agents import SequentialAgent, LoopAgent, ParallelAgent
from google.genai import types
from google.adk.sessions import InMemorySessionService
from google.adk.runners import Runner
from google.adk.tools.mcp_tool.mcp_toolset import MCPToolset, StdioServerParameters
from google.adk.tools import transfer_to_agent

import os
import asyncio

os.environ["GOOGLE_API_KEY"]=".........."

async def get_tools_async(run_command, arguments):
print(f"Connecting to MCP tool: command={run_command}, args={arguments}")
tools, exit_stack = await MCPToolset.from_server(
connection_params=StdioServerParameters(command=run_command, args=arguments),
# async_exit_stack=self.common_exit_stack
)
print(f"Connected and received {len(tools)} tools.")
return tools, exit_stack

async def create_agent(command, args, agent_name, agent_instruction):
"""Gets tools from MCP Server."""
tools, exit_stack = await get_tools_async(command, args)

agent = LlmAgent(
model='gemini-2.0-flash',
name=agent_name,
instruction=agent_instruction,
tools=tools,
)
return agent, exit_stack

async def main():
itinerary, exit_stack1 = await create_agent("npx", ["@gongrzhe/server-travelplanner-mcp"], "ItineraryPlannerAgent", "Generate a travel itinerary with popular spots, optimized travel time, and meal breaks based on destination and duration. Return the plan in a daily breakdown in the response itself.")
airbnb, exit_stack2 = await create_agent("npx", ["-y","@openbnb/mcp-server-airbnb"], "StayBookingAgent", "Search for suitable Airbnb stays based on the travel query or the planned travel Itinerary. Return details like name, price, and availability in the response itself.")

root_agent = LlmAgent(
    model="gemini-2.0-flash",
    name="Agentic_Travel_Assistant",
    instruction="Automate end-to-end travel planning using individual agents for stay booking, itinerary planning. Each agent handles a specific task using MCP tools and contributes to building a complete travel plan. ItineraryPlannerAgent Agent uses 'travel-planner' tool to plan the trip and StayBookingAgent uses 'airbnb' tool to seach and pick an airbnb property according to the itinery planned.",
    sub_agents=[itinerary, airbnb]
)

session_service = InMemorySessionService()
session = session_service.create_session(app_name="travelplanner", user_id="user1", session_id="session1")
runner = Runner(agent=root_agent, app_name="travelplanner", session_service=session_service)

content = types.Content(role='user', parts=[types.Part(text="plan my trip to kerala from hyderabad, starting on 11th may 2025 and ending on 20th may 2025, my budget is 50k rupees, do not ask me any questions")])

events_async = runner.run_async(
    session_id=session.id, user_id=session.user_id, new_message=content
)

async for event in events_async:
    print(f"Event received: {event.content}")

await exit_stack1.aclose()
await exit_stack2.aclose()

if name == "main":
asyncio.run(main())`

Here is the error I am facing,

an error occurred during closing of asynchronous generator <async_generator object stdio_client at 0x...>
asyncgen: <async_generator object stdio_client at 0x...>

• Exception Group Traceback (most recent call last):
  | File "anyio/_backends/_asyncio.py", line 772, in aexit
  | raise BaseExceptionGroup(
  | exceptiongroup.BaseExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
  | Traceback (most recent call last):
  | File "mcp/client/stdio/init.py", line 173, in stdio_client
  | yield read_stream, write_stream
  | GeneratorExit
  +------------------------------------

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "mcp/client/stdio/init.py", line 166, in stdio_client
async with (
File "anyio/_backends/_asyncio.py", line 778, in aexit
if self.cancel_scope.exit(type(exc), exc, exc.traceback):
File "anyio/_backends/_asyncio.py", line 457, in exit
raise RuntimeError(
RuntimeError: Attempted to exit cancel scope in a different task than it was entered in

Traceback (most recent call last):
File "anyio/_backends/_asyncio.py", line 776, in aexit
raise exc_val
File "mcp/client/stdio/init.py", line 166, in stdio_client
async with (
File "anyio/abc/_resources.py", line 29, in aexit
await self.aclose()
File "anyio/_backends/_asyncio.py", line 1074, in aclose
await self.wait()
File "anyio/_backends/_asyncio.py", line 1082, in wait
return await self._process.wait()
File "asyncio/subprocess.py", line 134, in wait
return await self._transport._wait()
File "asyncio/base_subprocess.py", line 235, in _wait
return await waiter
asyncio.exceptions.CancelledError: Cancelled by cancel scope ...

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "test_agent.py", line 65, in
asyncio.run(main())
File "asyncio/runners.py", line 44, in run
return loop.run_until_complete(main)
File "asyncio/base_events.py", line 649, in run_until_complete
return future.result()
File "test_agent.py", line 60, in main
await exit_stack1.aclose()
File "contextlib.py", line 656, in aclose
await self.aexit(None, None, None)
File "contextlib.py", line 714, in aexit
raise exc_details[1]
File "contextlib.py", line 697, in aexit
cb_suppress = await cb(*exc_details)
File "mcp_tool/mcp_toolset.py", line 266, in aexit
await self._exit()
File "mcp_tool/mcp_toolset.py", line 234, in _exit
await self.exit_stack.aclose()
File "contextlib.py", line 656, in aclose
await self.aexit(None, None, None)
File "contextlib.py", line 714, in aexit
raise exc_details[1]
File "contextlib.py", line 697, in aexit
cb_suppress = await cb(*exc_details)
File "contextlib.py", line 217, in aexit
await self.gen.athrow(typ, value, traceback)
File "mcp/client/stdio/init.py", line 166, in stdio_client
async with (
File "anyio/_backends/_asyncio.py", line 778, in aexit
if self.cancel_scope.exit(type(exc), exc, exc.traceback):
File "anyio/_backends/_asyncio.py", line 465, in exit
raise RuntimeError(
RuntimeError: Attempted to exit a cancel scope that isn't the current tasks's current cancel scope

Exception ignored in: <function _ProactorBasePipeTransport.del at 0x...>
Traceback (most recent call last):
File "asyncio/proactor_events.py", line 116, in del
_warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
File "asyncio/proactor_events.py", line 80, in repr
info.append(f'fd={self._sock.fileno()}')
File "asyncio/windows_utils.py", line 102, in fileno
raise ValueError("I/O operation on closed pipe")
ValueError: I/O operation on closed pipe

Exception ignored in: <function BaseSubprocessTransport.del at 0x...>
Traceback (most recent call last):
File "asyncio/base_subprocess.py", line 125, in del
_warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
File "asyncio/base_subprocess.py", line 78, in repr
info.append(f'stdout={stdout.pipe}')
File "asyncio/proactor_events.py", line 80, in repr
info.append(f'fd={self._sock.fileno()}')
File "asyncio/windows_utils.py", line 102, in fileno
raise ValueError("I/O operation on closed pipe")
ValueError: I/O operation on closed pipe

I am not able to understand the whole error and where the error is occurring.

Please, suggest what can be done here.
Thanks