AgentPhone

Overview

AgentPhone, from Relay Innovations, Inc. (a Y Combinator company), gives AI agents phone numbers for voice calls and messaging through one REST API and one webhook. Standard US and Canada numbers handle voice, SMS and MMS. iMessage lines are a separate number type, and WhatsApp (through your own Business Account) and RCS Business Messaging are in beta.

Key features

• Voice calls in webhook mode (your server replies with text, streamed as NDJSON) or hosted mode (built-in AI from a system prompt), with call transfer, DTMF and live transcripts
• iMessage tapbacks, threaded replies, screen and bubble effects, group chats, typing indicators and chat backgrounds, with RCS or SMS fallback for non-Apple recipients
• Live iMessage, SMS and RCS capability check before sending
• One agent.message webhook for SMS, iMessage, WhatsApp and voice, signed with HMAC-SHA256
• TypeScript and Python SDKs, a hosted MCP server, a Vercel Chat SDK adapter, and LangChain, CrewAI and OpenAI Agents SDK tools
• Sub-accounts, 10DLC registration from the dashboard, OTP verification and browser web calls

Pricing

Pay as you go with $5 of starting credit: numbers $3 a month, voice $0.13 a minute over webhook or $0.22 hosted, SMS $0.02 a segment and MMS $0.03 in either direction, and call recording $5 a month per account. iMessage lines cost $150 a month inbound-only or $250 for a dedicated line that also sends, with no per-message charge. RCS and WhatsApp beta rates are on the pricing page.

How it compares to Linq

Both offer iMessage with RCS and SMS fallback, group chats and tapbacks. AgentPhone also places and answers voice calls through its API, while Linq's docs say its API does not place or answer calls. Linq bills a flat monthly fee from $260 with no per-message fees; AgentPhone bills iMessage per line and SMS and voice by usage. Linq reports SOC 2 Type II; AgentPhone reports SOC 2 Type I with Type II in progress.

Best for

Developers building AI agents that need voice calls and texting from one API, with iMessage lines added for blue bubbles.

Sources

• agentphone.ai
• agentphone.ai/llms.txt
• agentphone.ai/pricing
• agentphone.ai/trust
• agentphone.ai/terms
• agentphone.ai/privacy
• agentphone.ai/openapi.json
• docs.agentphone.to/llms.txt
• docs.agentphone.to/welcome
• docs.agentphone.to/documentation/guides/messages
• docs.agentphone.to/documentation/guides/whatsapp
• docs.agentphone.to/documentation/guides/rcs
• docs.agentphone.to/documentation/guides/calls
• docs.agentphone.to/documentation/guides/webhooks
• docs.agentphone.to/documentation/guides/phone-numbers
• docs.agentphone.to/documentation/reference/messaging-rate-limits
• docs.agentphone.to/documentation/reference/faq
• docs.agentphone.to/usage
• docs.agentphone.to/sub-accounts
• docs.agentphone.to/mcp
• docs.agentphone.to/integrations/vercel
• docs.agentphone.to/integrations/langchain
• docs.agentphone.to/integrations/sim
• docs.agentphone.to/api-reference/contact-cards/overview
• github.com/AgentPhone-AI