AIMessage enforces ToolCall model incompatible with openai

[yildirimgoks]

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Example Code

from langchain.messages import AIMessage, ToolCall

# OpenAI compatible tool call format
tool_call = {
   "id":"tc1",
   "type":"function",
   "function":{
      "name":"SomeTool",
      "arguments":"{\"some_argument\": \"some_value\"}"
   }
}

# line below works fine
ToolCall(**tool_call)

# line below returns an error
AIMessage(content="", tool_calls=[ToolCall(**tool_call)])

# error message:
# pydantic.v1.error_wrappers.ValidationError: 1 validation error for AIMessage
# tool_call() got an unexpected keyword argument 'function' (type=type_error)

Description

When you provide a value for the 'tool_calls' argument of the AIMessage, root_validator tries to parse the values in it to a ToolCall object using the langchain_core.messages.tool.tool_call function. Although instancing ToolCall by calling it directly with OpenAI compatible tool_calls model is possible, the tool_call() function expects a specific set of variables to build the ToolCall, and does not accept extra keyword variables. This enforces a very specific data model when tool_calls is provided with AIMessage and makes it impossible to create an AIMessage object with the desired tool_calls formatting.

Is this intended or could this be a bug? IIs there a different way of creating an AI message with tool_calls that I'm missing?

System Info

langchain==0.2.14
langchain-community==0.2.12
langchain-core==0.2.33
langchain-openai==0.1.22
langchain-text-splitters==0.2.2

Checked the latest source code & documentation and the issue persists in the most recent version as well.