Keep your existing agent.
Use an HTTP transcript-and-reply handler for voice. Your current tools and business logic stay in your backend instead of becoming a separate voice project.
See how it worksAgentPhone vs Vapi
Bring your own agent to the phone. A Vapi alternative built around your backend.
Your agent already has a model, memory, and tools. Give it managed phone numbers, live calls, and messaging while keeping its logic in your own application.
Start buildingFree migration from Vapi.
Your AI agent
AgentPhoneVoice
SMS / MMS
iMessage
WhatsAppBeta
RCSBeta
Keep building your agent.
We’ll handle the phone.
Get the number here too.
Provision US and Canadian voice/SMS numbers through AgentPhone. Calling and SMS use your AgentPhone account, including outbound calls and registered outbound SMS.
See how it worksContinue beyond the call.
Let the same agent follow up over SMS or iMessage, with WhatsApp and RCS available in beta. Read message history when it needs context.
See how it worksThe agent you built can do the setup.
AgentPhone’s API signup creates a starter agent and number alongside the account and key, after email verification. Connect your existing backend and give it the ability to call, text, and read conversations. Keep building your product around the agent you already have.
- 1Your agent starts signup
The API sends a code to your email.
- 2You verify your email
It gets the account, key, agent, and number.
- 3Give it work to do
Connect its tools through MCP or the API.
Agent signup requires email verification. US outbound SMS requires carrier registration; iMessage requires access approval. Calling is subject to account verification and funding requirements.
What changes when
you use AgentPhone.
Choose based on how you want to connect an existing agent, provision numbers, and add messaging.
| What matters | AgentPhone | Vapi |
|---|---|---|
| Calling numbers | Managed US/Canada numbers for inbound and outboundInbound and outbound work on the same managed US or Canadian number. | Free US inbound number; import for outbound/international ↗ |
| SMS setup | Use AgentPhone numbers; registration appliesYour agent texts from the same number it calls from. | Import an approved Twilio number for SMS chat ↗ |
| Your existing AI | HTTP transcript in, text response outA plain request and response; there is no model interface to emulate. | Custom LLM server with an OpenAI-style interface ↗ |
| Conversation state | Message threads with your custom metadataAttach your own IDs and context to each thread. | Chats with sessions and previousChatId ↗ |
| Agent onboarding | Signup API returns starter agent, number, and keyYour agent can request its own key; you confirm by email. | Create or copy an API key from the dashboard ↗ |
| Phone tools | MCP actions for calling, messaging, and conversation historyCalling, texting, and reading history come from one MCP server. | MCP actions for assistants, calls, and numbers ↗ |
Selected workflows from each platform’s documentation, checked 2026-09-22. Follow the source links for setup details and requirements.
A phone layer for your existing runtime.
Point AgentPhone at your backend. Voice turns arrive as text, and your replies become speech. Your agent can call its own tools before answering. If you prefer a hosted voice agent, start with a system prompt and connect a number. You have both paths in the same account.
One place to manage the conversation.
Give your agent tools to read threads, send messages, and retrieve call transcripts. AgentPhone supports voice, SMS, MMS, iMessage, WhatsApp, and RCS. WhatsApp and RCS are in beta; iMessage requires access approval. Message history and metadata are available through the API.
We’ll help you make the move. For free.
Bring your Vapi setup. We’ll help you connect your agent, plan the migration, and get started on AgentPhone. Volume pricing and price matching are available as you scale.
AgentPhone SMS includes carrier fees and taxes.
Your agent has work to do.
Give it a number.
Start building Bring your agent. We’ll help with the move.