AgentPhone

AgentPhone, built by Relay Innovations, Inc. and backed by Y Combinator, provides AI agents with dedicated US and Canadian phone numbers provisioned instantly via a single API call. It unifies voice and messaging into one webhook handler, letting agents call, text, and respond without requiring separate pipelines for each channel.

What It Is

AgentPhone is a telephony infrastructure layer designed specifically for AI agents rather than human users. Where general-purpose telecom platforms like Twilio offer low-level building blocks, AgentPhone bundles real-time transcription, text-to-speech, automatic conversation threading, and MCP (Model Context Protocol) support into a single agent-ready API. Developers point a webhook at their agent, and AgentPhone delivers both inbound voice calls and SMS messages in the same event format.

How the Unified Webhook Works

The core design decision is a single webhook format for both voice and messaging channels. When a call comes in, AgentPhone transcribes it in real time and forwards the text to the webhook. The agent replies with text, and AgentPhone converts that reply to speech for the caller. SMS messages arrive through the same handler in the same shape, so one piece of code handles both channels without branching logic.

Integration Paths

AgentPhone supports four integration methods:

• Python SDK (pip install agentphone)
• Node.js SDK
• REST API
• MCP server (npx agentphone-mcp)

The MCP server path lets Claude Code, Cursor, Windsurf, Cline, Zed, and any other MCP-compatible client provision numbers, send messages, and handle calls through native tool use without writing custom integration code. The homepage also lists integrations with Google ADK, LangChain, Vercel AI SDK (chat-sdk.dev), and sim.ai.

Target Use Cases

AgentPhone is built for autonomous agent workflows where a phone identity is required:

• AI receptionists and workers that need to receive and place calls
• Sales and lead follow-up agents that call prospects on behalf of a human
• 2FA and verification inboxes so autonomous agents can receive one-time codes from services like Stripe or GitHub
• On-call engineering flows where an agent needs to be reachable by phone
• Coding agents (e.g., OpenClaw/Hermes) that need a phone number to interact with external services

Ecosystem Position

The homepage lists logos for Google, LangChain, Replit, Vercel, Stripe, Alchemy, and Y Combinator as part of the "agent ecosystem" context. AgentPhone positions itself as complementary to these platforms rather than competitive, providing the telephony layer that agent frameworks lack natively. The FAQ explicitly contrasts AgentPhone with Twilio, noting that AgentPhone is purpose-built for AI agents with unified webhooks, threading, transcription, and MCP already included.

Current Status

AgentPhone is actively available and backed by Y Combinator. The product supports US and Canadian phone numbers at launch, with additional countries described as "coming soon." The MCP server, Python SDK, Node.js SDK, and REST API are all listed as current integration options on the live site.