Michael Brenndoerfer | Data & AI, Private Equity, Technology

Michael Brenndoerfer

Example: Adding a Calculator to Our Agent › Step 1: Create the Calculator Function

Michael BrenndoerferJune 29, 20252 min read

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Part 5 of 15Tool Use - Extending the Agent's Abilities

Chapter 14Example: Adding a Calculator to Our Agent › Step 1: Create the Calculator Function

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Section 3 of 16 · 2 min read

Example: Adding a Calculator to Our Agent › Step 1: Create the Calculator FunctionOne section · Sections in this chapter3 / 16 ↓

Sections in this chapter16

First, we need a Python function that performs calculations. We'll use Python's built-in eval() function to evaluate mathematical expressions:

In[3]:

Code

def calculate(expression: str) -> dict:
    """
    Evaluate a mathematical expression and return the result.
    
    Args:
        expression: A math expression like "1234 * 5678" or "100 + 50 - 25"
    
    Returns:
        Dictionary with 'result' or 'error'
    """
    try:
        # Evaluate the expression
        result = eval(expression)
        return {
            "success": True,
            "result": result,
            "expression": expression
        }
    except Exception as e:
        return {
            "success": False,
            "error": str(e),
            "expression": expression
        }

This function takes a string like "1234 * 5678", evaluates it, and returns the result in a structured format. We include error handling so the agent can provide helpful messages if something goes wrong.

Let's test it:

In[4]:

Code

## Test the calculator
print(calculate("1234 * 5678"))
print(calculate("100 + 50 - 25"))
print(calculate("10 / 3"))

Out[4]:

Console

{'success': True, 'result': 7006652, 'expression': '1234 * 5678'}
{'success': True, 'result': 125, 'expression': '100 + 50 - 25'}
{'success': True, 'result': 3.3333333333333335, 'expression': '10 / 3'}

{'success': True, 'result': 7006652, 'expression': '1234 * 5678'}
{'success': True, 'result': 125, 'expression': '100 + 50 - 25'}
{'success': True, 'result': 3.3333333333333335, 'expression': '10 / 3'}

Perfect. Our calculator works. Now we need to connect it to the agent.

Security Note

Using eval() on untrusted input is dangerous in production. It can execute arbitrary Python code. For this educational example, it's fine since only the agent (not users directly) calls this function. In production, use a safe math parser like ast.literal_eval() or a dedicated math library.