Voice Agent Builder Pro

Build and manage Voice AI agents using Vapi, Bland.ai, or Retell. Create agents, configure voices, set prompts, make outbound calls, and retrieve transcripts...

Security Scan

The skill largely matches a Vapi wrapper (it needs only VAPI_API_KEY and calls api.vapi.ai) but the README/skill instructions claim broader multi-platform functionality and include commands not implemented in the shipped script — the mismatch and the fact that the tool will transmit third‑party credentials (e.g., Twilio SID/AuthToken) to Vapi deserve caution.

Purpose & Capability

The skill's name/description and the included Python wrapper align: it is a Vapi API client and legitimately requires VAPI_API_KEY. However, SKILL.md repeatedly claims support for Bland.ai and Retell and lists broader platform integrations and features that are not implemented in the provided script (the code only talks to https://api.vapi.ai). That overstatement is an incoherence between purpose/marketing and actual capability.

Instruction Scope

Runtime instructions expect you to pass potentially sensitive third‑party credentials (e.g., Twilio account SID and auth token) as JSON arguments to import-phone; the script will forward those values to Vapi's API. The SKILL.md also documents commands (e.g., create-kb) and integration patterns (calendar, CRM, Bland.ai/Retell) that are either not present in the CLI router or are only described at a conceptual level. In short: the instructions encourage transmitting credentials to the remote Vapi API and claim behaviors the code does not implement.

Install Mechanism

No install spec — instruction-only with a single Python script. Nothing is downloaded or installed automatically by the skill package itself, which minimizes install-time risk.

Credentials

Only one environment variable is required: VAPI_API_KEY, which is proportionate for a wrapper around the Vapi API. However, operational instructions direct users to supply other service credentials (e.g., Twilio SID/AuthToken) via CLI arguments; these will be transmitted to the Vapi service and so are sensitive. The skill does not request other unrelated environment variables, which is good.

Persistence & Privilege

The skill does not request 'always: true' and does not include installation hooks that modify other skills or system settings. It behaves as a normal user-invokable skill.

What to consider before installing

This package is essentially a Vapi API client and needs only your VAPI_API_KEY — that part is coherent. However: (1) SKILL.md overstates support for Bland.ai/Retell and documents commands (like create-kb) that aren't implemented in the shipped script; treat those claims as marketing, not functionality. (2) Several example commands (import-phone) show you passing third-party credentials (Twilio SID/AuthToken) on the command line — the script will send those values to api.vapi.ai. Only provide such secrets if you trust Vapi and the skill author (agxntsix.ai). (3) If you plan to use this in production, verify Vapi's security/BAA/compliance for any sensitive data (PHI/PCI), and consider using short‑lived or limited-scope credentials when possible. (4) If you need Bland.ai or Retell support, expect to supply separate, official integrations rather than relying on this skill. (5) To reduce risk: run the script in an isolated environment, monitor network calls (to ensure they go to the documented api.vapi.ai endpoint), and inspect or test with non-production credentials before supplying real accounts.

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":"[phone]"}}'

# 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":"[phone]","twilioAccountSid":"AC...","twilioAuthToken":"..."}'

5. Call Handling

Outbound calls:

python3 {baseDir}/scripts/vapi_agent.py call '{"assistantId":"asst_xxx","phoneNumberId":"pn_xxx","customer":{"number":"[phone]"}}'

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)

1. Voice agent qualifies lead on call
2. Use Vapi's serverUrl webhook to capture call data
3. On call end → create/update GHL contact
4. Move opportunity to appropriate pipeline stage
5. Schedule follow-up if needed

Voice + Calendar Booking

1. Agent checks availability via calendar API
2. Uses function calling to book appointment
3. Confirms date/time verbally
4. 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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