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

# Core Concepts

> Learn the fundamental building blocks of sondos-ai.com, including system prompts, voices, and AI assistants

Welcome to the fundamentals of sondos-ai.com. Here, we explore the essential building blocks that you need to understand before configuring your AI assistant and calls.

## 1. System Prompt & Initial Message

**System Prompt**

* The "brain" of your AI assistant. You write a short (or long) set of instructions that guide the assistant's behavior and tone of voice.
* This includes any important business info, disclaimers, or how you want the AI to handle edge cases.
* For example: *"You are a helpful phone assistant for XYZ Company, you greet in a friendly manner, confirm the caller's info, etc."*

**Initial Message**

* The very first thing the AI says.
* Typically short, like "Hello, thanks for calling XYZ Company!"

## 2. Voices

* sondos-ai.com integrates with **ElevenLabs** voices for natural-sounding speech.
* You can **clone** your own voice by providing audio samples or pick from built-in voices.
* Each voice can have adjustable parameters like speech speed, filler usage, or accent (if available).

## 3. Putting It All Together

* An **AI Assistant** is built by combining a system prompt, an initial message, and a chosen voice.
* Optionally, you add tools (like "transfer call" or "end call").
* Once the assistant is set, you assign it to a phone number (for inbound) or a campaign (for outbound).

**Next Steps**

* Learn how [call minutes and billing](/getting-started/understanding-billing) work to plan your usage.
* Or, jump to [AI Assistants Overview](/ai-assistants/what-is-ai-assistant) to start building your first assistant.