dvcrn Voice Agent Builder
Build, configure, and manage Voice AI agents. Supports Vapi (primary), Bland.ai, and Retell platforms.
Quick Start
export VAPI_API_KEY="your-vapi-api-key"
# Create a voice agent
python3 {baseDir}/scripts/vapi_agent.py create-agent '{"name":"Sales Agent","firstMessage":"Hi! How can I help you today?","systemPrompt":"You are a helpful sales assistant for Acme Corp."}'
# Make an outbound call
python3 {baseDir}/scripts/vapi_agent.py call '{"assistantId":"asst_xxx","phoneNumberId":"pn_xxx","customer":{"number":"+15551234567"}}'
# List agents
python3 {baseDir}/scripts/vapi_agent.py list-agents
# List calls
python3 {baseDir}/scripts/vapi_agent.py list-calls
Platform Comparison
| Feature | Vapi | Bland.ai | Retell |
|---|---|---|---|
| Best For | Custom agents, dev-friendly | Simple outbound campaigns | Enterprise, low latency |
| Latency | ~800ms | ~500ms | ~500ms |
| Languages | 100+ | 30+ | 30+ |
| Custom LLM | ✅ Any OpenAI-compatible | ✅ Limited | ✅ Via API |
| Phone Numbers | Buy/import | Buy/import | Buy/import |
| Pricing | $0.05/min + provider costs | $0.09/min all-in | $0.07-0.15/min |
| WebSocket | ✅ | ❌ | ✅ |
| Knowledge Base | ✅ Built-in | ✅ | ✅ |
| Transfers | ✅ | ✅ | ✅ |
Recommendation: Start with Vapi — most flexible, best docs, largest community. Use Bland for simple high-volume outbound. Use Retell for enterprise low-latency needs.
See {baseDir}/scripts/voice_comparison.md for detailed breakdown.
Agent Creation Workflow
1. Choose a Voice
Vapi supports multiple TTS providers:
- ElevenLabs — Best quality, most natural (recommended)
- PlayHT — Good quality, lower cost
- Deepgram — Fast, good for real-time
- Azure — Enterprise, many languages
2. Configure the Agent
{
"name": "Appointment Setter",
"firstMessage": "Hi! This is Sarah from Dr. Smith's office. I'm calling to help you schedule your appointment.",
"systemPrompt": "You are Sarah, a friendly appointment scheduler...",
"voice": {
"provider": "11labs",
"voiceId": "21m00Tcm4TlvDq8ikWAM"
},
"model": {
"provider": "openai",
"model": "gpt-4o",
"temperature": 0.7
},
"endCallFunctionEnabled": true,
"maxDurationSeconds": 300,
"silenceTimeoutSeconds": 30
}
3. Prompt Engineering for Voice
Voice prompts differ from text. Key principles:
- Keep responses SHORT — 1-2 sentences max per turn
- Be conversational — use filler words naturally ("Sure thing!", "Got it!")
- Handle interruptions — voice agents get cut off, design for it
- Confirm understanding — repeat back key info (names, numbers, dates)
- Include fallback — "I didn't catch that, could you repeat?"
4. Phone Number Setup
# List available phone numbers
python3 {baseDir}/scripts/vapi_agent.py list-phones
# Buy a number (via Vapi dashboard or API)
# Import existing number (Twilio, Vonage)
python3 {baseDir}/scripts/vapi_agent.py import-phone '{"provider":"twilio","number":"+15551234567","twilioAccountSid":"AC...","twilioAuthToken":"..."}'
5. Call Handling
Outbound calls:
python3 {baseDir}/scripts/vapi_agent.py call '{"assistantId":"asst_xxx","phoneNumberId":"pn_xxx","customer":{"number":"+15551234567"}}'
Inbound: Assign agent to phone number in Vapi dashboard, or via API:
python3 {baseDir}/scripts/vapi_agent.py update-phone '{"id":"pn_xxx","assistantId":"asst_xxx"}'
Integration Patterns
Voice + CRM (GHL)
- Voice agent qualifies lead on call
- Use Vapi's
serverUrlwebhook to capture call data - On call end → create/update GHL contact
- Move opportunity to appropriate pipeline stage
- Schedule follow-up if needed
Voice + Calendar Booking
- Agent checks availability via calendar API
- Uses function calling to book appointment
- Confirms date/time verbally
- Sends SMS confirmation after call
Voice + Knowledge Base
Upload documents to Vapi's knowledge base for RAG:
python3 {baseDir}/scripts/vapi_agent.py create-kb '{"name":"Product FAQ","files":["faq.pdf"]}'
Available Commands
python3 {baseDir}/scripts/vapi_agent.py create-agent '{...}' # Create new agent
python3 {baseDir}/scripts/vapi_agent.py get-agent <id> # Get agent details
python3 {baseDir}/scripts/vapi_agent.py list-agents # List all agents
python3 {baseDir}/scripts/vapi_agent.py update-agent <id> '{...}' # Update agent
python3 {baseDir}/scripts/vapi_agent.py delete-agent <id> # Delete agent
python3 {baseDir}/scripts/vapi_agent.py call '{...}' # Make outbound call
python3 {baseDir}/scripts/vapi_agent.py get-call <id> # Get call details
python3 {baseDir}/scripts/vapi_agent.py list-calls # List all calls
python3 {baseDir}/scripts/vapi_agent.py list-phones # List phone numbers
python3 {baseDir}/scripts/vapi_agent.py import-phone '{...}' # Import phone number
python3 {baseDir}/scripts/vapi_agent.py update-phone '{...}' # Update phone config
Credits
Built by M. Abidi | agxntsix.ai YouTube | GitHub Part of the AgxntSix Skill Suite for OpenClaw agents.
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