AI Voice Agent Calling API
Give your AI agents real phone numbers — inbound and outbound calls, BYO AI model
Developer-friendly REST API for AI-powered phone calls. You bring the AI — we handle telephony, billing, numbers, recordings, and call management.
The BubblyPhone AI Voice Agent API gives developers a programmatic way to connect AI agents to real phone calls — purchase phone numbers, handle inbound and outbound voice, transcribe conversations, record audio, and let your AI use tools mid-call, all through a simple REST API.
Unlike closed voice AI platforms, BubblyPhone is BYOK: bring any LLM (OpenAI, Anthropic, Google, or your own model) and any voice provider. Two integration modes fit any architecture — Webhook Mode for full control over conversation flow, or Streaming Mode for sub-second real-time audio bridging with models like Gemini 3.1 Flash Live and GPT Realtime.
Prepaid per-minute billing starts at $0.04/min inbound, $0.05/min outbound, with phone numbers from $3/month and coverage across 200+ countries.
import bubblyphone
client = bubblyphone.Client(api_key="your_api_key")
# 1. Buy a phone number
number = client.numbers.purchase(country="US")
# 2. Point it at your AI via webhook
client.numbers.configure(
number.id,
webhook_url="https://your-app.com/ai-handler",
)
# 3. Incoming calls now hit your AI.
# Transcripts, recordings, and billing are handled for you.Control BubblyPhone from your AI coding agent
Open-source MCP server works with Claude Code, Claude Desktop, Cursor, Codex, and any MCP-compatible client. Make calls, manage numbers, and check usage — without leaving your editor.
{
"mcpServers": {
"bubblyphone": {
"command": "npx",
"args": ["@bubblyphone/mcp-server"],
"env": {
"BUBBLYPHONE_API_KEY": "bp_live_sk_your_key_here"
}
}
}
}- make_call — initiate outbound calls from your AI
- list_calls / get_call — query call history and details
- get_call_transcript — fetch transcripts mid-conversation
- inject_context — steer a live call with new instructions
- search_phone_numbers / purchase_number — manage numbers
- get_usage / get_billing — check spend without leaving your editor
Prefer remote? Point any MCP client at https://agents.bubblyphone.com/mcp
How It Works
Get a number
Purchase a phone number via API. From $3/month.
Configure
Set a webhook URL or choose streaming mode with your AI model.
AI handles calls
Incoming calls hit your AI. Transcripts, recordings, and billing handled.
Everything you need to build voice AI
A complete toolkit for AI voice agents — numbers, calls, recordings, and safety controls.
Bring Your Own AI
Any LLM. Any STT. Any TTS. No vendor lock-in.
Transcription
Real-time transcripts for every call.
Call Recording
Automatic recording with API access.
Tool Use
AI can call functions mid-conversation.
Budget Controls
Per-key budgets, hard and soft limits.
Rate Limiting
Per-key rate limits + IP whitelisting.
200+ Countries
Global coverage with transparent rates.
API Keys
Multiple keys with scoped permissions.
Two ways to handle calls
Choose the integration style that fits your architecture
You control everything
Events sent to your endpoint. You respond with actions. Works with any stack.
- • Full control over conversation flow
- • Use any LLM, any logic
- • Simple HTTP request-response
We connect your AI directly
Real-time audio bridge between caller and your AI model. Sub-second latency.
- • Gemini 3.1 Flash Live, GPT Realtime, and more
- • Tool calling for actions
- • BYOK — use your own API key
What developers are building
Common use cases for AI phone agents
Simple, transparent pricing
Pay as you go. No contracts. No minimums.
Outbound calls
$0.05/min
Inbound calls
$0.04/min
Phone numbers (US)
$3/mo
BYOK (Bring Your Own Key) — use your own LLM API key and skip model charges. International numbers available from $5/mo. See full pricing →
Why developers choose BubblyPhone
No vendor lock-in
BYOK. Use any model, switch anytime. Your AI, your infrastructure.
No minimum spend
Prepaid credit. Top up $10 or $5,000. No contracts, cancel anytime.
Two integration modes
Webhook for full control. Streaming for simplicity. Choose what fits.
Frequently Asked Questions
What is the BubblyPhone AI voice agent API?
A REST API that lets developers give their AI agents real phone numbers. Your AI can make outbound calls, answer inbound calls, record conversations, and use tools mid-call. You bring the LLM and voice models; BubblyPhone handles telephony, billing, and call management.
Can I control BubblyPhone from Claude Code, Cursor, or Codex?
Yes. BubblyPhone ships an open-source MCP (Model Context Protocol) server that plugs into Claude Code, Claude Desktop, Cursor, Codex, and any MCP-compatible client. You can make calls, manage phone numbers, check billing, fetch transcripts, and inject context into live calls — all from your coding agent.
How does BYOK (Bring Your Own Key) work?
You provide your own API key for your LLM (OpenAI, Anthropic, Google, etc.) and voice models. BubblyPhone never charges you for model inference — you pay your AI vendor directly at their rates and pay us only for the phone call minutes and numbers.
What's the difference between Webhook Mode and Streaming Mode?
Webhook Mode sends call events to your HTTP endpoint and you respond with actions — full control, works with any stack. Streaming Mode opens a real-time audio bridge between the caller and your AI model (Gemini 3.1 Flash Live, GPT Realtime, etc.) with sub-second latency and built-in tool calling.
Which LLMs and voice models are supported?
Any model with an API. Streaming Mode has first-class support for Gemini 3.1 Flash Live, GPT Realtime, and other realtime voice models. Webhook Mode works with any LLM you can call over HTTP.
How is billing calculated?
Prepaid credit, pay-as-you-go. $0.05/min outbound calls, $0.04/min inbound calls, $3/mo for US phone numbers (international from $5/mo). No monthly fees, no minimum spend, no contracts.
Can I record and transcribe calls?
Yes. Every call can be automatically recorded and transcribed. Recordings are accessible via API, transcripts are generated in real-time and stored alongside each call.
Which countries are supported?
200+ countries for outbound calls. Phone numbers available in the US, UK, EU, and other major markets.
How do I get started?
Sign up at agents.bubblyphone.com/register (free, no credit card required), generate an API key, purchase a phone number, and make your first call.
Ready to give your AI a phone number?
Start building in minutes. No credit card required.