Voice Integration

Build AI-powered phone agents using Twilio and ElevenLabs.

Overview

Voice integration uses two providers:

Together they power Voice Agents that can make and receive phone calls.

Setup

1. Twilio (Phone Numbers)

Twilio provides the phone infrastructure for making and receiving calls.

1. Create a Twilio (opens in a new tab) account
2. Get your Account SID and Auth Token from the console
3. Purchase phone number(s) for your account
4. In Lux Desktop: Settings → Credentials → Add Credential
5. Select Twilio and enter your credentials

2. ElevenLabs (AI Voice)

ElevenLabs provides the AI voice synthesis that powers your voice agents.

Note: Lux uses a platform ElevenLabs key for voice agents. You don't need your own ElevenLabs account unless you want custom voices.

For custom voices:

1. Create an ElevenLabs (opens in a new tab) account
2. Get your API key
3. In Lux Desktop: Settings → APIs → ElevenLabs
4. Enter your API key

Phone Numbers

Viewing Numbers

lux va twilio-numbers

Number Types

Inbound Configuration

Configure a number to receive calls:

lux va configure-inbound +15551234567 flow_xyz

This routes incoming calls to your flow.

Making Outbound Calls

Via Flow (Voice Agent Node)

{
  "agentId": "va_support",
  "to": "+15559876543",
  "from": "+15551234567",
  "variables": {
    "customerName": "John",
    "issueType": "billing"
  }
}

Via CLI

lux va call va_123 +15559876543 --from +15551234567

Handling Inbound Calls

Flow Setup

Inbound Call Trigger
       ↓
   Check Business Hours
       ↓
   If (open)
     ├── Yes → Voice Agent
     └── No → Play Message → Hang Up

Inbound Call Variables

When a call comes in:

{
  "callSid": "CA123...",
  "from": "+15559876543",
  "to": "+15551234567",
  "direction": "inbound"
}

Voice Selection

ElevenLabs provides natural-sounding voices:

Custom Voices

You can also use custom voices from your ElevenLabs account.

Voice Settings

Fine-tune voice output:

{
  "stability": 0.5,       // Voice consistency (0-1)
  "similarity": 0.75,     // Match to original (0-1)
  "speed": 1.0           // Speaking rate (0.5-2)
}

Call Handling

Call Duration

Set maximum call duration:

{
  "maxDuration": 300  // 5 minutes in seconds
}

Call Transfer

Transfer to a human when needed:

// In voice agent prompt
"If the customer asks for a human agent, transfer them to the support line."

Built-in transfer tool:

{
  "tool": "transfer",
  "destination": "+15551234567"
}

End Call

Voice agents can end calls:

// In voice agent prompt
"When the conversation is complete, thank them and end the call."

Post-Call Data

After calls complete, you receive:

{
  "callSid": "CA123...",
  "duration": 127,
  "status": "completed",
  "transcript": [...],
  "collectedData": {...}
}

Process this in a post-call flow to:

• Store transcripts
• Update CRM
• Send follow-up emails
• Analyze sentiment

Pricing

Twilio Voice

ElevenLabs

Best Practices

Voice Agent Prompts

• Keep responses short for natural conversation
• Handle interruptions gracefully
• Include clear call endings

Phone Numbers

• Use local numbers for better answer rates
• Consider toll-free for inbound
• Follow local regulations

Quality

• Test in quiet environments
• Monitor call transcripts
• Iterate on prompts based on calls

See Also:

• Voice Agents
• SMS Integration