LangChain

apiVersion: v1
runtime: python3.12
entrypoint: agent.py:executor
dependencies: requirements.txt

langchain-classic>=1.0
langchain-openai>=1.0

from langchain_classic.agents import AgentExecutor, create_tool_calling_agent
from langchain_core.prompts import ChatPromptTemplate
from langchain_core.tools import tool
from langchain_openai import ChatOpenAI


@tool
def word_count(text: str) -> int:
    """Counts the words in a piece of text."""
    return len(text.split())


# Reads OPENAI_API_KEY, which you add as a secret on the agent's Config tab.
model = ChatOpenAI(model="gpt-5")
prompt = ChatPromptTemplate.from_messages([
    ("system", "Count the words in what the user says, then answer."),
    ("human", "{input}"),
    ("placeholder", "{agent_scratchpad}"),
])
executor = AgentExecutor(agent=create_tool_calling_agent(model, [word_count], prompt), tools=[word_count])