Building custom tools in Agentic AI

Introduction

Building custom tools helps you create smart helpers that do specific jobs for you. It makes your AI more useful and fits your unique needs.

You want your AI to answer questions about your own documents.

You need the AI to perform special tasks like booking appointments or checking your calendar.

You want to add new abilities to your AI that it doesn't have by default.

You want to connect your AI to other apps or websites to get real-time data.

You want to control how the AI works by giving it clear instructions and tools.

Syntax

Agentic AI

class CustomTool:
    def __init__(self, name, description, func):
        self.name = name
        self.description = description
        self.func = func

    def run(self, input_data):
        return self.func(input_data)

# Example usage:
# def my_tool_function(data):
#     # process data
#     return result

# tool = CustomTool('ToolName', 'What this tool does', my_tool_function)
# output = tool.run(input_data)

Define a class or function that wraps your tool's logic.

Give your tool a clear name and description so the AI knows when to use it.

Examples

A simple function that says hello to a given name.

Agentic AI

def greet(name):
    return f"Hello, {name}!"

A tool class that calculates math expressions given as strings.

Agentic AI

class MathTool:
    def __init__(self):
        pass
    def run(self, expression):
        return eval(expression)

Creating a tool instance and running it with input 'Alice'.

Agentic AI

tool = CustomTool('Greet', 'Says hello to someone', greet)
print(tool.run('Alice'))

Sample Model

This program builds a custom tool that reverses any text you give it. It shows how to define the tool, create it, and use it.

Agentic AI

class CustomTool:
    def __init__(self, name, description, func):
        self.name = name
        self.description = description
        self.func = func

    def run(self, input_data):
        return self.func(input_data)

# Define a tool function that reverses text

def reverse_text(text):
    return text[::-1]

# Create the tool
reverse_tool = CustomTool('ReverseText', 'Reverses the input text', reverse_text)

# Use the tool
input_string = 'hello world'
output = reverse_tool.run(input_string)
print(f"Input: {input_string}")
print(f"Output: {output}")

Important Notes

Make sure your tool functions are simple and do one clear job.

Test your tools separately before connecting them to your AI agent.

Keep tool descriptions clear so the AI can pick the right tool when needed.

Summary

Custom tools let you add special skills to your AI.

Each tool has a name, description, and a function that does the work.

Use tools to make your AI smarter and more helpful for your tasks.

Practice

1. What is the main purpose of building custom tools for an AI agent?

easy

A. To change the AI's language automatically

B. To add special skills that help the AI perform specific tasks

C. To reduce the size of the AI model

D. To make the AI run faster on any computer

Solution

1. Step 1: Understand what custom tools do

   Custom tools add new abilities or skills to an AI, making it better at certain jobs.

2. Step 2: Compare options to the purpose

   Only To add special skills that help the AI perform specific tasks talks about adding special skills, which matches the purpose of custom tools.

3. Final Answer:

   To add special skills that help the AI perform specific tasks -> Option B

4. Quick Check:

   Custom tools = add special skills [OK]

Hint: Custom tools add new skills to AI for tasks [OK]

Common Mistakes:

• Thinking custom tools speed up AI generally
• Confusing tool purpose with model size
• Assuming tools change AI language automatically

2. Which of the following is the correct way to define a custom tool in Python for an AI agent?

easy

A. tool = Tool(name='search', func=search_function)

B. tool = Tool('search', func=search_function)

C. tool = Tool(description='Find info', func=search_function)

D. tool = Tool(name='search', description='Find info', func=search_function)

Solution

1. Step 1: Recall required fields for a custom tool

   A custom tool needs a name, description, and a function to work properly.

2. Step 2: Check which option includes all three

   Only tool = Tool(name='search', description='Find info', func=search_function) has name, description, and func parameters correctly set.

3. Final Answer:

   tool = Tool(name='search', description='Find info', func=search_function) -> Option D

4. Quick Check:

   Tool needs name, description, and func [OK]

Hint: Include name, description, and func when defining tools [OK]

Common Mistakes:

• Omitting description or name
• Passing parameters in wrong order
• Using wrong parameter names

3. Given this Python code for a custom tool, what will be the output when calling tool.func('hello')?

def shout(text):
    return text.upper() + '!!!'
tool = Tool(name='shout', description='Make text loud', func=shout)

medium

A. 'HELLO!!!'

B. 'hello!!!'

C. 'hello'

D. Error: func is not callable

Solution

1. Step 1: Understand the function behavior

   The function shout converts text to uppercase and adds three exclamation marks.

2. Step 2: Apply the function to 'hello'

   Calling shout('hello') returns 'HELLO!!!'. Since tool.func points to shout, tool.func('hello') does the same.

3. Final Answer:

   'HELLO!!!' -> Option A

4. Quick Check:

   shout('hello') = 'HELLO!!!' [OK]

Hint: Check function logic and apply input to predict output [OK]

Common Mistakes:

• Ignoring uppercase conversion
• Missing exclamation marks
• Assuming func is not callable

4. You wrote this custom tool but get an error when using it. What is the likely problem?

def add_numbers(a, b):
    return a + b
tool = Tool(name='adder', description='Add two numbers', func=add_numbers)
result = tool.func(5)

medium

A. Tool name must be unique

B. Function add_numbers should not return a value

C. Missing one argument when calling tool.func

D. Description is too short

Solution

1. Step 1: Check function parameters

   add_numbers requires two inputs: a and b.

2. Step 2: Check how tool.func is called

   tool.func(5) provides only one argument, causing an error for missing the second argument.

3. Final Answer:

   Missing one argument when calling tool.func -> Option C

4. Quick Check:

   Function needs 2 args, only 1 given [OK]

Hint: Match function parameters with call arguments [OK]

Common Mistakes:

• Ignoring function argument count
• Thinking description length causes error
• Assuming tool name uniqueness causes runtime error

5. You want to build a custom tool that summarizes text by returning the first 10 words. Which code correctly defines this tool's function?

hard

A. def summarize(text):
return ' '.join(text.split()[:10])

B. def summarize(text):
return text[:10]

C. def summarize(text):
return text.split()[-10:]

D. def summarize(text):
return len(text.split())

Solution

1. Step 1: Understand the goal of the function

   The function should return the first 10 words, not characters or last words.

2. Step 2: Analyze each option

   def summarize(text): return ' '.join(text.split()[:10]) splits text into words and joins the first 10 words correctly. def summarize(text): return text[:10] returns first 10 characters, not words. def summarize(text): return text.split()[-10:] returns last 10 words. def summarize(text): return len(text.split()) returns word count, not summary.

3. Final Answer:

   def summarize(text): return ' '.join(text.split()[:10]) -> Option A

4. Quick Check:

   First 10 words = def summarize(text): return ' '.join(text.split()[:10]) [OK]

Hint: Split text and join first 10 words for summary [OK]

Common Mistakes:

• Returning characters instead of words
• Taking last words instead of first
• Returning word count instead of summary