# Voice Agent Builder

The Voice Agent Builder is the environment for creating phone-based AI agents that handle inbound and outbound calls.

[![Voice Agent Builder — overview](../images/voice-agent-overview.png)](../images/voice-agent-overview.png)

A Voice Agent uses speech-to-text (STT) to transcribe what a caller says, passes the transcript to a language model (LLM) for reasoning, and speaks the response back using text-to-speech (TTS) — all in real time over a telephony connection.

Use Voice Agent when you need:

- **Phone-based interactions** — the agent must receive or place calls via a phone number.
- **Real-time speech processing** — conversations happen over voice, not text.
- **Outbound campaigns** — the agent places calls to a list of contacts on a defined schedule.
- **Inbound call handling** — the agent answers incoming calls and routes or resolves them autonomously.

For text-based chat agents, use the [Chatbot Builder](../8_chatbot_builder/index.html) instead. For multi-step reasoning workflows over APIs and data sources, use the [Agentic Flow Builder](../9_agentic_flow_builder/index.html).