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AI + SMS

Let Claude or ChatGPT
send SMS from your phone.

With the Unlimited Messaging MCP server and the free Android app, an AI assistant writes and sends text messages from your own SIM card, checks whether they arrived, reads the replies, and asks you before every send.

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The idea

How does an AI assistant send an SMS?

An AI assistant sends an SMS by calling a tool on an MCP server: it decides to call the tool with a phone number and a text, the server queues the message, and your Android phone sends it from its SIM card over your carrier's network.

Unlimited Messaging is that MCP server. Its send-message tool already covered WhatsApp and email; since 7 November 2026 it also takes SMS, sent by the Unlimited Messaging Android app from your own number and on your own plan. The recipient gets an ordinary text from you, not from a short code or an unknown number.

The same connector reads, too. list-messages filters by channel, so the assistant can tell you whether a text was delivered, or sum up the replies. SMS received after you sign in to the app land in the same inbox as your WhatsApp chats and emails.

It works with any MCP client that supports remote servers with OAuth: Claude (claude.ai, Desktop and mobile), ChatGPT on the plans that offer custom connectors, Cursor, Claude Code.

Setup guides per assistant: Claude, ChatGPT. Comparing gateway apps? Android SMS gateway apps compared.

Illustration: a grid of small icons with one highlighted, with the headline “Your AI assistant texts from your phone”.

Setup

From zero to a first SMS sent by your assistant

  1. 01

    Create your account

    Sign up on Unlimited Messaging. The free plan is enough to try; its messages end with "Sent with UnlimitedMessaging.app".

  2. 02

    Install the Android app

    Download the APK on your phone (Android 8.0 or newer), sign in through the website's own login page and grant the SMS permissions. Each SIM becomes an SMS account.

  3. 03

    Add the connector

    In Claude or ChatGPT, add a custom connector with the URL https://mcp.unlimitedmessaging.app and approve access through OAuth.

  4. 04

    Ask in plain words

    "Text Marie that I'm 10 minutes late." The assistant drafts the SMS, shows it to you, and sends it once you say yes.

Examples

Prompts that work

Real requests, and what the assistant does with each one.

  1. "Text Marie at +33 6 12 34 56 78: running 10 minutes late, start without me."

    One send-message call with the SMS channel. The assistant shows the exact text and the number, then sends after you confirm.

  2. "Send tomorrow's three patients an SMS reminder with their time, from my work SIM."

    It calls list-accounts to find your SMS accounts, picks the work SIM's accountId and drafts one message per person, so you can check each one.

  3. "Did the plumber get my text? What did he answer?"

    list-messages filtered on SMS. You get the status (delivered only if your carrier sends delivery reports) and the reply, if one came in.

  4. "Send Paul the venue address by WhatsApp and by SMS, in case he has no data."

    A single call with two channels. The same text goes out on WhatsApp and as an SMS, each with its own status.

  5. "Summarize the texts I got today and draft replies. Don't send anything."

    Read-only: the assistant lists today's SMS, groups them by sender and writes drafts you can send later, or not.

Under the hood

What the assistant actually sends

The MCP tool call behind the first prompt uses the same fields as the REST API, so what an assistant can do, your code can do too.

send-messageJSON
{
  "to": {
    "phone": "+33612345678"
  },
  "channels": [
    {
      "channel": "SMS"
    }
  ],
  "text": "I'm running 10 minutes late, start without me."
}
Arguments of the send-message tool, as the assistant fills them. Add "accountId" in the channel entry to choose a SIM.
POST /messageShell
curl https://api.unlimitedmessaging.app/message \
  -H "Authorization: Bearer $UM_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"to":{"phone":"+33612345678"},"channels":[{"channel":"SMS"}],"text":"Running 10 minutes late."}'
The same SMS from your own code, with an API key instead of OAuth.

Safety

Built-in guardrails

Texting from your number stays under your control. Three guardrails take care of it.

  1. It asks before sending

    The Unlimited Messaging MCP server tells assistants to confirm before every send, and Claude and ChatGPT also show the tool call for your approval. Keep that approval on for send-message.

  2. People, not campaigns

    It is designed for reminders and conversations. Unlimited Messaging spaces SMS out to respect Android's pacing, and consumer plans exclude bulk marketing, so mailing lists belong elsewhere.

  3. Access you can take back

    Remove the connector in your assistant's settings to cut its access. Sign out of the Android app and no SMS leaves your phone any more.

FAQ

Questions about AI assistants sending SMS

Sources

Sources & references

To check the information in this article for yourself:

  1. Model Context Protocol - official documentationModel Context Protocol
  2. About custom connectors and remote MCP serversClaude - Anthropic Help Center
  3. Model Context Protocol & connectorsOpenAI
  4. Unlimited Messaging for Android - README (permissions, statuses)GitHub - UnlimitedMessaging
  5. SmsUsageMonitor (30 SMS in 30 minutes threshold)Android Open Source Project
  6. MFMessageComposeViewController (user must tap send on iOS)Apple Developer Documentation
Ilian, senior software engineer

Written by

· Senior Software Engineer

A senior software engineer, he founds and runs several tech companies. He builds products around messaging APIs, automation and AI integration, and shares here what he learns while building.

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Give your assistant a phone number: yours.

Install the free Android app, add the connector in Claude or ChatGPT, and ask for your first text.

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