---
title: Agents overview
description: Understand VaniAgent voice engines, configuration areas, and the agent lifecycle.
---

An agent combines a conversation engine, voice, instructions, knowledge, call controls, and post-call analysis. Provider-specific settings remain isolated, so switching an engine does not silently copy incompatible values.

## Choose an engine

| Engine | Pipeline | Best for | Key controls |
| --- | --- | --- | --- |
| **Classic Pipeline** | Speech-to-text → LLM → text-to-speech | Broad provider and voice choice | TTS provider, voice, language, speed, transcription languages |
| **Vani Ultra** | Whisper → Gemma → OmniVoice | VaniAgent-managed multilingual voice calls | Vani Ultra voice, vocabulary, language, generation steps |
| **Ultra Realtime** | Gemini Live speech-to-speech | Low-latency natural conversation | Gemini voice, realtime language, provider-specific prompt |

## Configuration map

1. **Identity** — name, active state, assigned phone number, and optional avatar.
2. **Conversation** — fixed or variable greeting, fallback greeting, system prompt, and engine-specific prompt.
3. **Knowledge** — attach one or more published knowledge bases.
4. **Speech** — voice, language, speed, transcription languages, and pronunciation vocabulary.
5. **Call behaviour** — interruptions, background music, and hard call-duration limit.
6. **Analysis** — default, structured, or advanced post-call extraction.
7. **Advanced flow** — optional flow PDL with `off`, `shadow`, or `active` runtime mode.

:::caution
Always test after changing the engine, greeting, prompt, knowledge, or assigned number. A saved configuration can still be unsuitable for real callers.
:::

## Agent lifecycle

Create the agent, configure its engine, test it in the browser or with a controlled call, attach a phone number, then activate it for inbound calls or campaigns. Deactivate an agent before major production changes if it is already receiving traffic.

## Post-call analysis

- **Default** produces the standard call summary and outcome.
- **Structured** extracts explicitly configured fields for predictable workflows.
- **Advanced** uses a custom analysis prompt and configuration.

Analysis is separate from the live conversation prompt. Changing analysis instructions does not alter what the caller hears.