fix: typing.Union Instantiation Error in Tool Usage (OpenAI Version Fix)

[Ilevk]

Description

• When I try to use tools, a TypeError occurs. This is a known issue, and it can be resolved by downgrading the OpenAI package to a version below 1.99.1.
  • TypeError: Cannot instantiate typing.Union
  • TypeError: Cannot instantiate typing.Union openai/openai-agents-python#1411
• simplify wallet initialization, remove redundant initialize

Tests

Before

Prompt: tell me my usdc balance in my account
Traceback (most recent call last):
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/chatbot.py", line 97, in <module>
    asyncio.run(main())
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/nest_asyncio.py", line 30, in run
    return loop.run_until_complete(task)
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/nest_asyncio.py", line 98, in run_until_complete
    return f.result()
  File "/Users/dable/.local/share/uv/python/cpython-3.10.13-macos-aarch64-none/lib/python3.10/asyncio/futures.py", line 201, in result
    raise self._exception.with_traceback(self._exception_tb)
  File "/Users/dable/.local/share/uv/python/cpython-3.10.13-macos-aarch64-none/lib/python3.10/asyncio/tasks.py", line 232, in __step
    result = coro.send(None)
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/chatbot.py", line 90, in main
    await run_chat_mode(agent=agent)
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/chatbot.py", line 49, in run_chat_mode
    output = await agent.run(user_input, message_history=history)
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/pydantic_ai/agent.py", line 562, in run
    async for _ in agent_run:
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/pydantic_ai/agent.py", line 2178, in __anext__
    next_node = await self._graph_run.__anext__()
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/pydantic_graph/graph.py", line 809, in __anext__
    return await self.next(self._next_node)
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/pydantic_graph/graph.py", line 782, in next
    self._next_node = await node.run(ctx)
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/pydantic_ai/_agent_graph.py", line 299, in run
    return await self._make_request(ctx)
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/pydantic_ai/_agent_graph.py", line 359, in _make_request
    model_response = await ctx.deps.model.request(message_history, model_settings, model_request_parameters)
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/pydantic_ai/models/openai.py", line 244, in request
    response = await self._completions_create(
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/pydantic_ai/models/openai.py", line 311, in _completions_create
    openai_messages = await self._map_messages(messages)
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/pydantic_ai/models/openai.py", line 466, in _map_messages
    tool_calls.append(self._map_tool_call(item))
  File "/Users/dable/Desktop/Base/dev/agentkit/python/examples/pydantic-ai-cdp-chatbot/.venv/lib/python3.10/site-packages/pydantic_ai/models/openai.py", line 485, in _map_tool_call
    return chat.ChatCompletionMessageToolCallParam(
  File "/Users/dable/.local/share/uv/python/cpython-3.10.13-macos-aarch64-none/lib/python3.10/typing.py", line 957, in __call__
    result = self.__origin__(*args, **kwargs)
  File "/Users/dable/.local/share/uv/python/cpython-3.10.13-macos-aarch64-none/lib/python3.10/typing.py", line 387, in __call__
    raise TypeError(f"Cannot instantiate {self!r}")
TypeError: Cannot instantiate typing.Union

After

Chatbot: python/examples/pydantic-ai-cdp-chatbot/chatbot.py
Network: Base Sepolia
Setup: Check USDC balance

Prompt:usdc balance 

---------------------------------
Your wallet 0xc3A5F395d8D626e0690199b15A9319db110cbE7E on base-sepolia holds 1 USDC (contract 0x036CbD53842c5426634e7929541eC2318f3dCF7e)
---------------------------------

Checklist

A couple of things to include in your PR for completeness:

• Added documentation to all relevant README.md files
• Added a changelog entry

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 1/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[phdargen]

Thanks for the fix @Ilevk, looks great!

Could you please revert the manual Changelog edit and instead use towncrier as described here: https://github.com/coinbase/agentkit/blob/main/CONTRIBUTING-PYTHON.md#changelog

Please run it inpython/framework-extensions/pydantic-ai

[Ilevk]

I've rebase with latest main branch and create change log as following guidance.