Agent voice
Set up one AI agent's voice conversations: its prompt, call voice, engine, transcriber, messages, limits and quick replies.
Where to find it
Voice › Agent voice
Open this screen
Steps
- Open Voice › Agent voice and pick the agent in AI agent at the top right.
- Edit Persona and model and System prompt if needed (see All agents for writing a prompt).
- Choose the call voice under Agent voice and press Play to hear it.
- Check Call engine and Conversation engine.
- Adjust Transcriber, Messages, Conversation and Limits.
- Press Save in the bar at the bottom. Discard changes puts the saved values back.
Settings on this screen
| Setting | What it does | Default |
|---|---|---|
| AI agent | Which agent the page edits. The choice carries over to the other AI pages. | The agent you used last, else the first |
| Persona and model | Persona name, role, tone, language, goals, rules and model; or start from the agent library or Build with AI. | — |
| System prompt | How the agent speaks and behaves on calls. Up to 200,000 characters. | — |
| Agent voice | The agent's call voice and its Speed, Stability and Similarity. | Same as the workspace voice |
| Call engine | Grok (Call's own call path) or Vapi. Vapi needs the operator's Vapi key. | Grok |
| Conversation engine | The model that holds the agent's call conversations. | Claude Haiku (Anthropic) |
| Transcriber | Language, Silence threshold and Noise sensitivity. | Detect automatically, 0.75 s, 50% |
| Messages | Opening message and Error message. | Empty |
| Conversation | Allow interruptions and End the call after silence. | On, 300 seconds |
| Limits | Calls at the same time, Longest call, Calls per day. | 20 calls, 15 minutes, no limit |
| Quick replies & prompts | Reusable replies and prompt snippets to insert into the prompt. | — |
Troubleshooting
There is no AI agent yet.
A workspace manager types a Name and presses Create the agent on this page.
Switching agents asks Discard unsaved changes?
Press Cancel and Save first, or Discard changes to switch without saving.
Tips
- A banner at the top says which of these settings live calls use today; the voice chosen here is always the voice calls use.
- Recordings and transcripts are in the call log; the Conversation card links there.
Good to know
- Members can read the settings; only workspace managers can change them.
Related how-tos
- Choose the agent's call voice Pick the voice an AI agent speaks with on calls and how it sounds.
- Conversation engine Choose the AI model that holds an agent's call conversations.
- Transcriber settings Set the language the agent listens for and how it decides the caller has finished speaking.
- Opening and error messages Write what the agent says first, and what it says when something goes wrong.
- Interruptions, silence and call limits Decide whether callers can talk over the agent, when a silent call ends, and how many and how long calls may be.
- Quick replies & prompts Keep reusable replies and prompt snippets and insert them into the agent's prompt.
- Run an agent's calls on Vapi Switched off until an operator turns it on Switch an agent's calls from Grok to the Vapi engine, set up its Vapi assistant and test it.
- All agents See every AI agent in your organisation, which phone lines each one answers, and open one to change it.
- Set an agent’s persona and model Give the agent a name to use on the phone, a role, a tone, goals and rules, and choose how fast or capable its model is.
- Edit an agent’s system prompt Change the instructions that tell the agent who it is, how it talks and what it may say.
- Start an agent from the agent library Fill an agent’s prompt and persona from a ready-made phone persona for your type of business.
- Write an agent’s prompt with Build with AI Describe the agent you need, by typing or by voice, and get a draft persona and system prompt to review.
- Suggested from your calls Ready-made prompt lines and script steps for cases callers raise again and again, from conversations you approved.