> ## Documentation Index
> Fetch the complete documentation index at: https://flow9.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Build your voice agent

> Configure the AI agent's model, voice, prompt, and call behavior — then test it with a live web call.

The **Voice** section of the campaign form is where your AI caller takes
shape. An **estimated cost per minute** badge updates as you pick options.

## The essentials

* **Model** — the AI model powering the conversation.
* **Voice** — the voice your contacts hear.
* **Language** — searchable picker; defaults to English (US).
* **System prompt** *(required)* — tells the agent what to say and how to
  behave. Start from a **persona template** (Outbound Sales & Reactivation,
  Appointment Booking) or write your own. If your campaign collects data, an
  auto-managed *"Information to collect"* block is inserted into the prompt —
  hit **Regenerate** after changing the fields.
* **Welcome message** — the agent's opening line when the call connects.
* **Personalization** — once an audience is selected, insert
  `{{merge}}` tokens (like the contact's name) into the prompt; tokens that
  don't exist in your contact data get flagged.

## Advanced settings

Collapsible panels on the right fine-tune behavior:

| Panel                  | What you control                                                                                                     |
| ---------------------- | -------------------------------------------------------------------------------------------------------------------- |
| **Speech**             | Speaking speed, creativity, interruption sensitivity, response delay, ambient sound                                  |
| **Call**               | Max duration, end-after-silence, **voicemail detection** — hang up silently or leave a message you write             |
| **Retry**              | Max attempts, interval between attempts, and which results trigger a retry (no answer, busy, voicemail, call failed) |
| **Post-call analysis** | A prompt that runs after each call to classify what happened                                                         |
| **Knowledge base**     | Facts, FAQs, and reference URLs the agent can draw on                                                                |
| **Transcription**      | Accuracy mode, vocabulary specialization, background-noise handling, boosted keywords                                |

## Test it live

Click **Test Campaign** once you have a name and system prompt. A floating
**Test Audio** panel opens (it doesn't block the form):

1. **Run Test** starts a live voice call in your browser — talk to the agent
   through your microphone.
2. The transcript streams turn by turn as you speak.
3. **End the Call** stops it; run it again as many times as you like.

The test uses your current, even unsaved, configuration — so you can tweak the
prompt and immediately hear the difference. No real contacts are called.