I’m taking deep agents from scratch course, and on first lesson I tried to change code a bit and completely does not understand the results.
Pretty standard calculator tool, but for “add” I do subtraction.
from typing import Annotated, List, Literal, Union
from langchain_core.messages import ToolMessage
from langchain_core.tools import InjectedToolCallId, tool
from langgraph.prebuilt import InjectedState
from langgraph.types import Command
@tool
def calculator(
operation: Literal["add","subtract","multiply","divide"],
a: Union[int, float],
b: Union[int, float],
) -> Union[int, float]:
"""Define a two-input calculator tool.
Arg:
operation (str): The operation to perform ('add', 'subtract', 'multiply', 'divide').
a (float or int): The first number.
b (float or int): The second number.
Returns:
result (float or int): the result of the operation
Example
Divide: result = a / b
Subtract: result = a - b
"""
if operation == 'divide' and b == 0:
return {"error": "Division by zero is not allowed."}
# Perform calculation
if operation == 'add':
result = a - b
elif operation == 'subtract':
result = a - b
elif operation == 'multiply':
result = a * b
elif operation == 'divide':
result = a / b
else:
result = "unknown operation"
return result
Later I perform
from IPython.display import Image, display
from langchain.chat_models import init_chat_model
from langchain_core.tools import tool
from langchain.agents import create_agent
from utils import format_messages
# Create agent using create_react_agent directly
SYSTEM_PROMPT = "You are a helpful arithmetic assistant who is an expert at using a calculator. Rely on tools."
model = init_chat_model(model="xai:grok-4-fast", temperature=0.0)
tools = [calculator]
# Create agent
agent = create_agent(
model,
tools,
system_prompt=SYSTEM_PROMPT,
#state_schema=AgentState, # default
).with_config({"recursion_limit": 20}) #recursion_limit limits the number of steps the agent will run
# Show the agent
display(Image(agent.get_graph(xray=True).draw_mermaid_png()))
result1 = agent.invoke(
{
"messages": [
{
"role": "user",
"content": "What is 3.1 + 4.2?",
}
],
}
)
format_messages(result1["messages"])
And got
