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from typing import Sequence
from langchain_core.language_models import BaseLanguageModel
from langchain_core.prompts.chat import ChatPromptTemplate
from langchain_core.runnables import Runnable, RunnablePassthrough
from langchain_core.tools import BaseTool
from langchain.agents.format_scratchpad.tools import (
format_to_tool_messages,
)
from langchain.agents.output_parsers.tools import ToolsAgentOutputParser
def create_tool_calling_agent(
llm: BaseLanguageModel, tools: Sequence[BaseTool], prompt: ChatPromptTemplate
) -> Runnable:
"""Create an agent that uses tools.
Args:
llm: LLM to use as the agent.
tools: Tools this agent has access to.
prompt: The prompt to use. See Prompt section below for more on the expected
input variables.
Returns:
A Runnable sequence representing an agent. It takes as input all the same input
variables as the prompt passed in does. It returns as output either an
AgentAction or AgentFinish.
Example:
.. code-block:: python
from langchain.agents import AgentExecutor, create_tool_calling_agent, tool
from langchain_anthropic import ChatAnthropic
from langchain_core.prompts import ChatPromptTemplate
prompt = ChatPromptTemplate.from_messages(
[
("system", "You are a helpful assistant"),
("placeholder", "{chat_history}"),
("human", "{input}"),
("placeholder", "{agent_scratchpad}"),
]
)
model = ChatAnthropic(model="claude-3-opus-20240229")
@tool
def magic_function(input: int) -> int:
\"\"\"Applies a magic function to an input.\"\"\"
return input + 2
tools = [magic_function]
agent = create_tool_calling_agent(model, tools, prompt)
agent_executor = AgentExecutor(agent=agent, tools=tools, verbose=True)
agent_executor.invoke({"input": "what is the value of magic_function(3)?"})
# Using with chat history
from langchain_core.messages import AIMessage, HumanMessage
agent_executor.invoke(
{
"input": "what's my name?",
"chat_history": [
HumanMessage(content="hi! my name is bob"),
AIMessage(content="Hello Bob! How can I assist you today?"),
],
}
)
Prompt:
The agent prompt must have an `agent_scratchpad` key that is a
``MessagesPlaceholder``. Intermediate agent actions and tool output
messages will be passed in here.
"""
missing_vars = {"agent_scratchpad"}.difference(
prompt.input_variables + list(prompt.partial_variables)
)
if missing_vars:
raise ValueError(f"Prompt missing required variables: {missing_vars}")
if not hasattr(llm, "bind_tools"):
raise ValueError(
"This function requires a .bind_tools method be implemented on the LLM.",
)
llm_with_tools = llm.bind_tools(tools)
agent = (
RunnablePassthrough.assign(
agent_scratchpad=lambda x: format_to_tool_messages(x["intermediate_steps"])
)
| prompt
| llm_with_tools
| ToolsAgentOutputParser()
)
return agent
|