langchain/templates/openai-functions-agent/openai_functions_agent/agent.py

from typing import List, Tuple

from langchain.agents import AgentExecutor
from langchain.agents.format_scratchpad import format_to_openai_function_messages
from langchain.agents.output_parsers import OpenAIFunctionsAgentOutputParser
from langchain.chat_models import ChatOpenAI
from langchain.prompts import ChatPromptTemplate, MessagesPlaceholder
from langchain.tools.render import format_tool_to_openai_function
from langchain.tools.tavily_search import TavilySearchResults
from langchain.utilities.tavily_search import TavilySearchAPIWrapper
from langchain_core.messages import AIMessage, HumanMessage
from langchain_core.pydantic_v1 import BaseModel, Field

# Create the tool
search = TavilySearchAPIWrapper()
description = """"A search engine optimized for comprehensive, accurate, \
and trusted results. Useful for when you need to answer questions \
about current events or about recent information. \
Input should be a search query. \
If the user is asking about something that you don't know about, \
you should probably use this tool to see if that can provide any information."""
tavily_tool = TavilySearchResults(api_wrapper=search, description=description)

tools = [tavily_tool]

llm = ChatOpenAI(temperature=0)
assistant_system_message = """You are a helpful assistant. \
Use tools (only if necessary) to best answer the users questions."""
prompt = ChatPromptTemplate.from_messages(
    [
        ("system", assistant_system_message),
        MessagesPlaceholder(variable_name="chat_history"),
        ("user", "{input}"),
        MessagesPlaceholder(variable_name="agent_scratchpad"),
    ]
)

llm_with_tools = llm.bind(functions=[format_tool_to_openai_function(t) for t in tools])


def _format_chat_history(chat_history: List[Tuple[str, str]]):
    buffer = []
    for human, ai in chat_history:
        buffer.append(HumanMessage(content=human))
        buffer.append(AIMessage(content=ai))
    return buffer


agent = (
    {
        "input": lambda x: x["input"],
        "chat_history": lambda x: _format_chat_history(x["chat_history"]),
        "agent_scratchpad": lambda x: format_to_openai_function_messages(
            x["intermediate_steps"]
        ),
    }
    | prompt
    | llm_with_tools
    | OpenAIFunctionsAgentOutputParser()
)


class AgentInput(BaseModel):
    input: str
    chat_history: List[Tuple[str, str]] = Field(
        ..., extra={"widget": {"type": "chat", "input": "input", "output": "output"}}
    )


agent_executor = AgentExecutor(agent=agent, tools=tools, verbose=True).with_types(
    input_type=AgentInput
)