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Parallel tool use

In the Chains with multiple tools guide we saw how to build function-calling chains that select between multiple tools. Some models, like the OpenAI models released in Fall 2023, also support parallel function calling, which allows you to invoke multiple functions (or the same function multiple times) in a single model call. Our previous chain from the multiple tools guides actually already supports this.


We'll need to install the following packages for this guide:

%pip install --upgrade --quiet langchain-core

If you'd like to trace your runs in LangSmith uncomment and set the following environment variables:

import getpass
import os

# os.environ["LANGCHAIN_TRACING_V2"] = "true"
# os.environ["LANGCHAIN_API_KEY"] = getpass.getpass()


from import tool

def multiply(first_int: int, second_int: int) -> int:
"""Multiply two integers together."""
return first_int * second_int

def add(first_int: int, second_int: int) -> int:
"Add two integers."
return first_int + second_int

def exponentiate(base: int, exponent: int) -> int:
"Exponentiate the base to the exponent power."
return base**exponent

API Reference:


Install dependencies
pip install -qU langchain-openai
Set environment variables
import getpass
import os

os.environ["OPENAI_API_KEY"] = getpass.getpass()
from langchain_openai import ChatOpenAI

llm = ChatOpenAI(model="gpt-3.5-turbo-0125")
from operator import itemgetter
from typing import Dict, List, Union

from langchain_core.messages import AIMessage
from langchain_core.runnables import (

tools = [multiply, exponentiate, add]
llm_with_tools = llm.bind_tools(tools)
tool_map = { tool for tool in tools}

def call_tools(msg: AIMessage) -> Runnable:
"""Simple sequential tool calling helper."""
tool_map = { tool for tool in tools}
tool_calls = msg.tool_calls.copy()
for tool_call in tool_calls:
tool_call["output"] = tool_map[tool_call["name"]].invoke(tool_call["args"])
return tool_calls

chain = llm_with_tools | call_tools
"What's 23 times 7, and what's five times 18 and add a million plus a billion and cube thirty-seven"
[{'name': 'multiply',
'args': {'first_int': 23, 'second_int': 7},
'id': 'call_22tgOrsVLyLMsl2RLbUhtycw',
'output': 161},
{'name': 'multiply',
'args': {'first_int': 5, 'second_int': 18},
'id': 'call_EbKHEG3TjqBhEwb7aoxUtgzf',
'output': 90},
{'name': 'add',
'args': {'first_int': 1000000, 'second_int': 1000000000},
'id': 'call_LUhu2IT3vINxlTc5fCVY6Nhi',
'output': 1001000000},
{'name': 'exponentiate',
'args': {'base': 37, 'exponent': 3},
'id': 'call_bnCZIXelOKkmcyd4uGXId9Ct',
'output': 50653}]

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