This tutorial provides a step-by-step guide to creating an SMS API using the Mezzio PHP framework and Twilio's PHP SDK. To start, you need to create a new Mezzio application, install required dependencies, and add your Twilio credentials. Next, you'll create classes for sending SMS, including `TwilioService` and `SMSData`, which will be used to validate the phone number and message body. The tutorial also covers refactoring the route's handler class to use these new classes and configurations. Finally, it includes a testing section where you can run the application using Composer's built-in web server and send an SMS using Curl. The process culminates in a fully functional Mezzio application that sends SMS using Twilio.