> ## Documentation Index
> Fetch the complete documentation index at: https://docs.itellico.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Calculator

> Use the built-in Calculator tool for math during live conversations

<Badge>Expert Mode</Badge>

## Overview

The **Calculator** tool lets your agent perform mathematical calculations during a conversation.

Add it from **Tools** → **Add** → **Calculator**.

## Availability

* Built-in tool with no external integration required
* Singleton tool per agent: if one Calculator already exists, the add-menu item is disabled

***

## Current Configuration

Calculator has no advanced setup form.

When you add it, the tool is created with:

* **Name:** `Calculator`
* **Description:** `Perform mathematical calculations`

You can reopen the dialog to keep or delete the tool, but there are no extra fields to configure today.

***

## Supported Calculations

The Calculator evaluates safe mathematical expressions. It supports:

* arithmetic operators: `+`, `-`, `*`, `/`, `//`, `%`, `**`
* parentheses for grouping
* functions: `abs`, `round`, `min`, `max`, `sum`, `sqrt`, `ceil`, `floor`, `log`, `log10`, `sin`, `cos`, `tan`
* constants: `pi`, `e`

There is no special percent operator. Express percentages as arithmetic, such as `price * 0.2` for 20% of a price.

<Note>
  Calculator expressions are capped at 200 characters and do not support symbolic math, derivatives, integrals, or arbitrary code execution.
</Note>

Use your prompt to tell the agent when it should rely on Calculator instead of answering from memory.

***

## Recommended Prompt Pattern

```text theme={null}
When the caller asks for a total, discount, repayment amount, or percentage,
use the Calculator tool before answering.

Always state the result clearly and confirm the currency or units if relevant.
```

***

## Good Use Cases

* quoting totals after discounts or fees
* calculating installment amounts
* comparing percentage changes
* converting simple pricing logic into a precise spoken answer

Use **Custom Action** instead if the value must come from your backend, CRM, billing system, or another source of truth.

***

## Testing Checklist

1. Add the tool in **Expert Mode**.
2. Run a test conversation.
3. Ask the agent to solve a few realistic calculations.
4. Confirm the spoken answer matches the expected value.
5. Check that the agent still explains the result in business language, not just raw numbers.

***

## Next Steps

* [Tools Overview](/build/tools/overview)
* [Custom Action](/build/tools/custom-api-actions)
* [Prompt Engineering Guide](/build/conversation/prompt-engineering-guide)