[sdk:python] TypeError when using ToolboxClient with async context manager in LangChain example

[dpf202507]

Prerequisites

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Question

I'm encountering an error when trying to use the ToolboxClient from toolbox_langchain in an async application with LangGraph and LangChain.
Why am I getting the error that 'ToolboxClient' object does not support the asynchronous context manager protocol?

Configuration:
OS: Windows

Unclosed client session
client_session: <aiohttp.client.ClientSession object at 0x000001EC998FEF90>
Traceback (most recent call last):
File "d:\2025.7\mcp toolbox\langchain_.py", line 55, in
asyncio.run(run_application())
File "D:\Program Files\miniconda\envs\langchain\Lib\asyncio\runners.py", line 195, in run
return runner.run(main)
File "D:\Program Files\miniconda\envs\langchain\Lib\asyncio\runners.py", line 118, in run
return self.loop.run_until_complete(task)
File "D:\Program Files\miniconda\envs\langchain\Lib\asyncio\base_events.py", line 725, in run_until_complete
return future.result()
File "d:\2025.7\mcp toolbox\langchain.py", line 44, in run_application
async with ToolboxClient("http://127.0.0.1:5000") as client:
TypeError: 'ToolboxClient' object does not support the asynchronous context manager protocol

Code

My tools.yaml configuration:

sources:
  my-mysql-source:
    kind: mysql
    host: 127.0.0.1
    port: 3306
    database: tool
    user: root1
    password: 2152911111

tools:
  search-hotels-by-name:
    kind: mysql-sql
    source: my-mysql-source
    description: Search for hotels based on name.
    parameters:
      - name: name
        type: string
        description: The name of the hotel.
    statement: SELECT * FROM hotels WHERE name LIKE CONCAT('%', ?, '%');

  search-hotels-by-location:
    kind: mysql-sql
    source: my-mysql-source
    description: Search for hotels based on location.
    parameters:
      - name: location
        type: string
        description: The location of the hotel.
    statement: SELECT * FROM hotels WHERE location LIKE CONCAT('%', ?, '%');

  book-hotel:
    kind: mysql-sql
    source: my-mysql-source
    description: Book a hotel by its ID.
    parameters:
      - name: hotel_id
        type: string
        description: The ID of the hotel to book.
    statement: UPDATE hotels SET booked = 1 WHERE id = ?;

  update-hotel:
    kind: mysql-sql
    source: my-mysql-source
    description: Update a hotel's check-in and check-out dates by its ID.
    parameters:
      - name: hotel_id
        type: string
        description: The ID of the hotel to update.
      - name: checkin_date
        type: string
        description: The new check-in date of the hotel.
      - name: checkout_date
        type: string
        description: The new check-out date of the hotel.
    statement: UPDATE hotels SET checkin_date = DATE(?), checkout_date = DATE(?) WHERE id = ?;

  cancel-hotel:
    kind: mysql-sql
    source: my-mysql-source
    description: Cancel a hotel by its ID.
    parameters:
      - name: hotel_id
        type: string
        description: The ID of the hotel to cancel.
    statement: UPDATE hotels SET booked = 0 WHERE id = ?;

toolsets:
  my-toolset:
    - search-hotels-by-name
    - search-hotels-by-location
    - book-hotel
    - update-hotel
    - cancel-hotel

Additional Details

code:

import os
import asyncio
from langgraph.prebuilt import create_react_agent
from langgraph.checkpoint.memory import MemorySaver
from toolbox_langchain import ToolboxClient
from langchain_openai import ChatOpenAI

prompt = """
  You're a helpful hotel assistant. You handle hotel searching, booking and
  cancellations. When the user searches for a hotel, mention it's name, id,
  location and price tier. Always mention hotel ids while performing any
  searches. This is very important for any operations. For any bookings or
  cancellations, please provide the appropriate confirmation. Be sure to
  update checkin or checkout dates if mentioned by the user.
  Don't ask for confirmations from the user.
"""

queries = [
    "Find hotels in Basel with Basel in it's name.",
    "Can you book the Hilton Basel for me?",
    "Oh wait, this is too expensive. Please cancel it and book the Hyatt Regency instead.",
    "My check in dates would be from April 10, 2024 to April 19, 2024.",
]

async def run_application():
    model = ChatOpenAI(
        api_key=os.getenv("DASHSCOPE_API_KEY"),
        base_url="https://dashscope.aliyuncs.com/compatible-mode/v1 ",
        model="qwen-plus",
    )

    async with ToolboxClient("http://127.0.0.1:5000") as client:
        tools = await client.aload_toolset()

        agent = create_react_agent(model, tools, checkpointer=MemorySaver())

        config = {"configurable": {"thread_id": "thread-1"}}
        for query in queries:
            inputs = {"messages": [("user", prompt + query)]}
            response = agent.invoke(inputs, stream_mode="values", config=config)
            print(response["messages"][-1].content)

asyncio.run(run_application())

[anubhav756]

Hi @dpf202507!

Thank you for creating this issue with such detailed information! We really appreciate you taking the time to provide the config and code, which helped us identify the problem quickly.

You are correct—the ToolboxClient did not properly support the async context manager protocol, which caused the TypeError you observed when using async with.

I have created a fix for this in PR #308, which adds full support for both sync (with) and async (async with) context management to ToolboxClient.

Additionally, we've rolled out similar improvements to other Toolbox SDKs to ensure a consistent developer experience there as well. (#307, #309)

The fix will be included in the next official package release.

Thanks again for your valuable contribution! 😃