AI agents have gotten remarkably capable. They write code, answer questions, manage calendars, and automate workflows. But most of them have the same limitation: they're stuck in text. They can't pick up a phone when someone calls. They can't make an outbound call when something urgent happens. They can't read a text a customer sends to their number.
This guide covers everything you need to know about getting a phone number for AI agents. Whether you're running OpenClaw, Hermes Agent, or something you built yourself, here's how to add voice and SMS in under 10 minutes.
What Is Agentic Calling?
Before we dive into phone numbers, let's talk about the concept behind them. Agentic calling is when an AI agent autonomously makes or receives phone calls as part of a workflow. It's not a chatbot on a phone line. It's an agent that decides when to call, what to say, and how to handle the conversation.
Think of it like this: traditional phone systems are human-driven. Someone picks up the phone, dials a number, and talks. Agentic calling flips that. The AI agent decides when a call needs to happen, initiates it, handles the conversation, and takes action based on what happens. Consequential actions need appropriate user authorization and oversight.
Examples of agentic calling: a new lead signs up and your AI agent calls them within 60 seconds. A server goes down at 3am and your agent calls the on-call engineer. A patient misses their appointment and your agent reschedules. A payment fails and your agent calls to update billing info before service gets cut off.
Agentic calling is one of the fastest-growing areas in AI infrastructure because it closes the loop between agents and the real world. For a deeper walkthrough of the stack, see The Complete Guide to AI Agent Voice Calling.
Phone Numbers for OpenClaw
OpenClaw is a powerful agent framework. It manages files, runs terminal commands, orchestrates workflows, and interacts with APIs. But it can't handle phone calls natively.
Getting an OpenClaw phone number with AgentLine takes 5 steps: sign up at agentline.cloud for an API key, install the AgentLine skill in OpenClaw, create an agent, buy a phone number (included in your plan), and start making calls.
The skill handles all telecom complexity: call routing, speech-to-text, text-to-speech, and number provisioning. Your OpenClaw agent sends text and receives text.
Building it yourself with Twilio takes weeks: provision a number, set up WebSocket media streams, integrate Deepgram or AssemblyAI for transcription, pipe responses through Cartesia or ElevenLabs for voice, and manage call state. Most OpenClaw users who tried DIY gave up at the WebSocket debugging phase. We break that tradeoff down in Why Twilio Is the Hard Way for AI Agents.
One OpenClaw user routes all customer calls through their agent. The agent authenticates callers, handles routine questions, and escalates complex issues to humans. They went from 200+ daily support calls to about 60 that actually need a person.
For a step-by-step OpenClaw-only setup, read OpenClaw Phone Numbers in 10 Minutes.
Phone Numbers for Hermes Agent
Hermes Agent has the same limitation: incredibly capable in text, no native voice support. You need a telephony layer.
AgentLine works identically with Hermes Agent: install the skill, set your API key, and your Hermes agent can immediately make outbound calls, receive inbound calls on a dedicated number, send and receive SMS, and read call transcripts.
A phone number for your Hermes agent lets it call you when server health checks fail instead of waiting for you to check a dashboard. Or call new leads within minutes of a contact form submission. Or handle customer support during off-hours.
The setup flow is identical regardless of agent framework — that's the advantage of a purpose-built AI telephony layer.
Phone Numbers for Any AI Agent
What if you built your own agent? AgentLine provides a REST API that any agent can call. Your agent creates an agent and buys a number through the API. For outbound calls, POST to /v1/calls. For inbound, AgentLine sends transcripts to your webhook. Your agent responds with text, AgentLine speaks it to the caller.
Any agent — LangChain, AutoGPT, custom Python, no-code — can have phone capabilities. No telecom protocols needed. Just HTTP requests. Developers who want code samples can follow the AgentLine API walkthrough.
The Voice API for AI Agents
AgentLine provides a voice API purpose-built for AI agents. Unlike Twilio or Vonage that expect you to build voice infrastructure, a purpose-built AI voice API handles: number provisioning, real-time speech-to-text, natural text-to-speech via Cartesia, call state management, and webhook-based event delivery.
For OpenClaw calling specifically, the skill wraps this API so you don't need direct HTTP calls. Tell your agent to call someone and the skill handles the rest.
The API supports programmatic access for custom integrations: curl -X POST https://api.agentline.cloud/v1/calls with your agent ID and the number to dial. One API call initiates the entire phone conversation.
SMS for AI Agents
Every AgentLine phone number handles voice and SMS in both directions. The agent can read texts people send to the number, including verification codes, and reply. For patterns and prompt tips, see SMS for AI Agents.
Real Use Cases for Agentic Calling
Customer support that never sleeps: Your AI agent answers 24/7, handles common questions, escalates complex issues. One SaaS team reduced support call volume from 200/day to 60/day.
Sales follow-up at speed: Leads contacted within 5 minutes convert at 3-4x the rate of later contacts. An AI agent calls every lead within 60 seconds.
Healthcare appointment reminders: No-shows cost healthcare billions. AI agents reduce no-show rates by 60-70%.
More concrete builds are covered in What You Can Build When Your AI Agent Has a Phone Number.
Getting Started
The entire setup: sign up at agentline.cloud, install the skill for your framework, buy a number (included in your plan), write a prompt, and make your first call. Under 10 minutes total. Pricing is simple: plans from $20/month include a number, minutes and SMS; beyond the plan it is $0.12 per minute, per-second after a one-minute minimum, $3.00/month per number, and $0.02 per SMS — see AgentLine pricing.
Choose a phone-number API
Before buying a number, compare provisioning, call handling and the number lifecycle in the US phone-number API buying guide. For hosted-call behavior and runtime tasks, use the updated voice-calling guide.