Your ADK Agent Can Now Make Phone Calls

AI agents can browse the web, write code, send emails, and query databases. But ask one to pick up the phone? Until now, that's where things got awkward.

A recent post mapping the full AI agent infrastructure stack (email, phone numbers, wallets, compute, voice) hit 156 upvotes and 88 comments on r/AI_Agents alone. The top comment captured the moment perfectly: "This is a great snapshot of the ecosystem. One thing that stands out is how much of this assumes ideal conditions. In practice, once agents start interacting with real users or messy inputs, things [break]."

That's exactly the problem. Voice is the most natural human interface, and it's been one of the hardest for AI agents to access. Building telephony into an agent typically meant wrangling Twilio credentials, configuring SIP trunks, managing WebRTC sessions, setting up webhook servers, and writing hundreds of lines of glue code before your agent could even say "hello."

We built AgentPhone to make that disappear. And today, we're excited to share that AgentPhone is now an official integration in Google's Agent Development Kit (ADK).

What This Actually Means

Google ADK is quickly becoming the go-to framework for building AI agents. It gives you multi-agent orchestration, tool use, memory, and a clean developer experience out of the box. But until now, if you wanted your ADK agent to handle voice calls or SMS, you were on your own.

The options weren't great. Retell AI, Bland AI, Synthflow, Vapi. There are over a dozen voice AI platforms out there, but most are built for enterprise call centers, not for a developer who just wants to give their agent a phone number. A recent Famulor breakdown compared pricing across 10 platforms. The complexity of just choosing is itself a problem.

AgentPhone fills that gap differently. Through a single MCP (Model Context Protocol) connection, any ADK agent can:

• Make and receive phone calls with full AI-powered voice conversations
• Send and receive SMS across managed phone numbers
• Buy and manage phone numbers with specific area codes
• Get complete call transcripts automatically after every conversation

No Twilio account. No webhook server. No telephony infrastructure to maintain. Just connect and go.

Agents Are Getting Full Identities. Phone Is the Hardest Part.

Something bigger is happening. Agents aren't just tools anymore. They're getting their own identities. Coinbase launched Agentic Wallets so agents can spend, earn, and trade autonomously. Ramp introduced Agent Cards with spending limits and approval workflows. EtherMail built moltmail for agent email accounts. The AI agents market is projected to hit $52.6 billion by 2030.

But among all these primitives (email, wallets, compute, payments), phone numbers generate the most friction. On r/Entrepreneur, a developer posted about giving AI agents their own phone numbers and got 22 comments of genuine feedback, questions, and edge cases. On r/gohighlevel, a UK-based builder hit a wall immediately: "I'm setting up voice AI agents and ran into something I didn't expect... the regulatory bundle says approval can take up to 72 hours." Just buying a number requires identity verification, regulatory approval, and sometimes days of waiting. All before writing a single line of agent logic.

AgentPhone exists because this shouldn't be hard.

What It Used to Take (vs. Now)

If you've ever tried to add telephony to an AI agent, you know the pain. A recent DEV Community tutorial on building a phone agent with ADK and Twilio is essentially a warning disguised as a how-to. The author walks through audio format mismatches (Twilio sends 8-bit, 8kHz μ-law; ADK expects 16-bit, 16kHz PCM), bidirectional media stream configuration, SIP trunking setup, and custom audio transcoding middleware. It's a full engineering project before your agent says a word.

Here's the typical journey without AgentPhone:

1. 1Sign up for a telephony provider. Verify your identity. Wait for approval.
2. 2Buy a number through their API. Configure it with webhooks.
3. 3Spin up a server to handle inbound call events.
4. 4Integrate a speech-to-text service. And a text-to-speech service. Separately.
5. 5Write the glue logic to pipe audio between your agent and the phone network.
6. 6Handle edge cases: call drops, silence detection, barge-in, timeouts.
7. 7Transcode between audio formats because nothing speaks the same encoding.
8. 8Deploy, monitor, and pray.

That's weeks of work. With AgentPhone + ADK, here's what it actually looks like:

import os
 
from google.adk.agents import Agent
from google.adk.tools.mcp_tool import McpToolset
from google.adk.tools.mcp_tool.mcp_session_manager import (
    StreamableHTTPConnectionParams,
)
 
AGENTPHONE_API_KEY = os.environ["AGENTPHONE_API_KEY"]
 
agent = Agent(
    model="gemini-2.5-pro",
    name="phone_agent",
    instruction="You handle phone calls and SMS for our business.",
    tools=[
        McpToolset(
            connection_params=StreamableHTTPConnectionParams(
                url="https://mcp.agentphone.ai/mcp",
                headers={"Authorization": f"Bearer {AGENTPHONE_API_KEY}"},
            )
        )
    ],
)

That's it. Your agent can now make calls, send texts, and manage phone numbers. The MCP server handles all the telephony complexity (voice synthesis, call routing, transcription) so your agent just focuses on the conversation.

What You Can Build

Here are a few ideas to get the wheels turning:

AI Receptionist

An agent that answers your business line 24/7, understands caller intent, books appointments, transfers to the right person, and sends a summary SMS after every call. No hold music. No "press 1 for sales." This is the use case that comes up most on r/AI_Agents. Builders want agents that can handle real inbound calls without human babysitting.

Outbound Follow-Up Agent

Pair it with a CRM. When a new lead comes in, the agent calls within minutes, qualifies interest, answers questions about your product, and books a meeting, all while your sales team sleeps. One r/Entrepreneur commenter put it simply: agents that can act outside the internet are "the missing piece."

Multi-Channel Support Agent

An ADK agent that handles support tickets via SMS and escalates to a live phone call when text isn't cutting it. Seamless channel-switching, same agent, same context.

Built on MCP

AgentPhone connects to ADK through the Model Context Protocol, the emerging open standard for giving AI agents access to tools and services. Think of MCP as USB-C for AI: one standard connection, and your agent gets access to everything AgentPhone offers.

Google recently launched an expanded ADK integrations ecosystem, and native MCP support is at the center of it. The McpToolset class handles all server interactions automatically. No custom middleware. No glue code.

This also means AgentPhone isn't locked to ADK. If you're building with Claude, Cursor, Windsurf, or any MCP-compatible client, the same integration works everywhere. But ADK's native MCP support makes the setup particularly clean.

Get Started

The AgentPhone integration is live in Google ADK today. Here's how to dive in:

• Read the full integration guide
• Explore the MCP server on GitHub
• Learn more about building agents with Google ADK