Creating tools for agents in LangChain - Practice Exercises

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this LangChain tool execution?

Consider this LangChain tool that adds two numbers. What will be the output when the tool is called with inputs 3 and 5?

LangChain

from langchain.tools import Tool

def add_numbers(a: int, b: int) -> int:
    return a + b

add_tool = Tool(
    name="Adder",
    func=add_numbers,
    description="Adds two numbers"
)

result = add_tool.func(3, 5)

A TypeError: func() missing 1 required positional argument

B 35

C 8

D None

💡 Hint

Think about what the add_numbers function returns when given 3 and 5.

The add_numbers function returns the sum of its two inputs. Calling add_tool.func(3, 5) returns 8.

📝 Syntax

intermediate

Which option correctly defines a LangChain tool with a synchronous function?

You want to create a LangChain tool that synchronously reverses a string. Which code snippet correctly defines this tool?

A reverse_tool = Tool(name="Reverser", func=lambda s: s[::-1], description="Reverses a string")

B reverse_tool = Tool(name="Reverser", async def func(s): return s[::-1], description="Reverses a string")

C reverse_tool = Tool(name="Reverser", func=async lambda s: s[::-1], description="Reverses a string")

D reverse_tool = Tool(name="Reverser", func=lambda s: s.reverse(), description="Reverses a string")

💡 Hint

Remember that synchronous functions do not use async keywords.

Option A defines a synchronous lambda function that returns the reversed string slice. Options A and C incorrectly use async syntax. Option A tries to call list.reverse() on a string, which is invalid.

🔧 Debug

advanced

What error does this LangChain tool code raise?

This tool is intended to fetch current weather but has a bug. What error will it raise when called?

LangChain

from langchain.tools import Tool
import requests

def get_weather(city: str) -> str:
    response = requests.get(f"https://api.weather.com/{city}")
    return response.json()['temp']

weather_tool = Tool(name="Weather", func=get_weather, description="Gets weather")

result = weather_tool.func('London')

A No error, returns temperature as string

B TypeError: func() missing 1 required positional argument

C requests.exceptions.ConnectionError

D KeyError: 'temp'

💡 Hint

Check what keys the JSON response might have and if 'temp' exists.

The code assumes the JSON response has a 'temp' key, but if the API returns a different structure or error, accessing 'temp' raises KeyError.

❓ state_output

advanced

What is the value of 'counter' after running this LangChain tool multiple times?

This tool increments a counter each time it is called. What is the value of 'counter' after calling tool.func() three times?

LangChain

from langchain.tools import Tool

counter = 0

def increment_counter() -> int:
    global counter
    counter += 1
    return counter

increment_tool = Tool(name="Incrementer", func=increment_counter, description="Increments counter")

increment_tool.func()
increment_tool.func()
increment_tool.func()

A 1

B 3

C 0

D TypeError: global variable not defined

💡 Hint

Think about how the global variable 'counter' changes with each call.

Each call to increment_counter increases the global counter by 1. After three calls, counter is 3.

🧠 Conceptual

expert

Which option best describes the role of a Tool in LangChain agents?

In LangChain, what is the primary purpose of creating a Tool for an agent?

A To provide a reusable function with a description that an agent can call to perform specific tasks during its reasoning process

B To store large datasets that the agent uses internally for training

C To handle user interface rendering for the agent

D To replace the language model with a faster alternative

💡 Hint

Think about how agents use tools to extend their capabilities.

Tools in LangChain are functions with descriptions that agents can call to perform tasks like calculations, API calls, or data retrieval during their reasoning.