Using a Calculator Tool with Claude
In this recipe, we'll demonstrate how to provide Claude with a simple calculator tool that it can use to perform arithmetic operations based on user input. We'll define the calculator tool and show how Claude can interact with it to solve mathematical problems.
Step 1: Set up the environment
First, let's install the required libraries and set up the Claude API client.
%pip install anthropicfrom anthropic import Anthropic
client = Anthropic()
MODEL_NAME = "claude-opus-4-1"Step 2: Define the calculator tool
We'll define a simple calculator tool that can perform basic arithmetic operations. The tool will take a mathematical expression as input and return the result.
Note that we are calling eval on the outputted expression. This is bad practice and should not be used generally but we are doing it for the purpose of demonstration.
import re
def calculate(expression):
# Remove any non-digit or non-operator characters from the expression
expression = re.sub(r"[^0-9+\-*/().]", "", expression)
try:
# Evaluate the expression using the built-in eval() function
# Note: eval is used here for demonstration purposes only.
# In production, use a safer alternative like ast.literal_eval or a math parser.
result = eval(expression) # noqa: S307
return str(result)
except (SyntaxError, ZeroDivisionError, NameError, TypeError, OverflowError):
return "Error: Invalid expression"
tools = [
{
"name": "calculator",
"description": "A simple calculator that performs basic arithmetic operations.",
"input_schema": {
"type": "object",
"properties": {
"expression": {
"type": "string",
"description": "The mathematical expression to evaluate (e.g., '2 + 3 * 4').",
}
},
"required": ["expression"],
},
}
]In this example, we define a calculate function that takes a mathematical expression as input, removes any non-digit or non-operator characters using a regular expression, and then evaluates the expression using the built-in eval() function. If the evaluation is successful, the result is returned as a string. If an error occurs during evaluation, an error message is returned.
We then define the calculator tool with an input schema that expects a single expression property of type string.
Step 3: Interact with Claude
Now, let's see how Claude can interact with the calculator tool to solve mathematical problems.
def process_tool_call(tool_name, tool_input):
if tool_name == "calculator":
return calculate(tool_input["expression"])
def chat_with_claude(user_message):
print(f"\n{'=' * 50}\nUser Message: {user_message}\n{'=' * 50}")
message = client.messages.create(
model=MODEL_NAME,
max_tokens=4096,
messages=[{"role": "user", "content": user_message}],
tools=tools,
)
print("\nInitial Response:")
print(f"Stop Reason: {message.stop_reason}")
print(f"Content: {message.content}")
if message.stop_reason == "tool_use":
tool_use = next(block for block in message.content if block.type == "tool_use")
tool_name = tool_use.name
tool_input = tool_use.input
print(f"\nTool Used: {tool_name}")
print(f"Tool Input: {tool_input}")
tool_result = process_tool_call(tool_name, tool_input)
print(f"Tool Result: {tool_result}")
response = client.messages.create(
model=MODEL_NAME,
max_tokens=4096,
messages=[
{"role": "user", "content": user_message},
{"role": "assistant", "content": message.content},
{
"role": "user",
"content": [
{
"type": "tool_result",
"tool_use_id": tool_use.id,
"content": tool_result,
}
],
},
],
tools=tools,
)
else:
response = message
final_response = next(
(block.text for block in response.content if hasattr(block, "text")),
None,
)
print(response.content)
print(f"\nFinal Response: {final_response}")
return final_responseStep 4: Try it out!
Let's try giving Claude a few example math questions now that it has access to a calculator.
chat_with_claude("What is the result of 1,984,135 * 9,343,116?")
chat_with_claude("Calculate (12851 - 593) * 301 + 76")
chat_with_claude("What is 15910385 divided by 193053?")==================================================
User Message: What is the result of 1,984,135 * 9,343,116?
==================================================
Initial Response:
Stop Reason: tool_use
Content: [ContentBlock(text='', type='text'), ContentBlockToolUse(id='toolu_01V2mzqp5qkB5QucRFjJUJLD', input={'expression': '1984135 * 9343116'}, name='calculator', type='tool_use')]
Tool Used: calculator
Tool Input: {'expression': '1984135 * 9343116'}
Tool Result: 18538003464660
[ContentBlock(text='Therefore, the result of 1,984,135 * 9,343,116 is 18,538,003,464,660.', type='text')]
Final Response: Therefore, the result of 1,984,135 * 9,343,116 is 18,538,003,464,660.
==================================================
User Message: Calculate (12851 - 593) * 301 + 76
==================================================
Initial Response:
Stop Reason: tool_use
Content: [ContentBlock(text='', type='text'), ContentBlockToolUse(id='toolu_01Mrrfy9adBzzxvhfZwnyJAe', input={'expression': '(12851 - 593) * 301 + 76'}, name='calculator', type='tool_use')]
Tool Used: calculator
Tool Input: {'expression': '(12851 - 593) * 301 + 76'}
Tool Result: 3689734
[ContentBlock(text='So the final result of evaluating the expression (12851 - 593) * 301 + 76 is 3689734.', type='text')]
Final Response: So the final result of evaluating the expression (12851 - 593) * 301 + 76 is 3689734.
==================================================
User Message: What is 15910385 divided by 193053?
==================================================
Initial Response:
Stop Reason: tool_use
Content: [ContentBlock(text='', type='text'), ContentBlockToolUse(id='toolu_01BfnN4LKp7oPRgmRzWeYdBG', input={'expression': '15910385 / 193053'}, name='calculator', type='tool_use')]
Tool Used: calculator
Tool Input: {'expression': '15910385 / 193053'}
Tool Result: 82.41459599177428
[ContentBlock(text='So 15910385 divided by 193053 equals 82.41459599177428.', type='text')]
Final Response: So 15910385 divided by 193053 equals 82.41459599177428.
'So 15910385 divided by 193053 equals 82.41459599177428.'