This extension has been merged into Matrix core as of version 6.16 and is no longer required to be installed separately.
Use Squiz Matrix as a headless CMS through the use of a powerful REST API web service.
The Content API extension for Squiz Matrix enables you to use Matrix as a headless CMS through a REST API web service.
Once installed, a new Content API Manager is available under System Management folder of the Matrix asset tree.
Here you can create new API tokens where you can restrict which parts of the asset tree are accessible to the API, as well as what permission restrictions the token should inherit based on a specific user.
The API also has built-in documentation that can be viewed within the Admin interface and shows all of the endpoints that are available and what data can be returned.
Please refer to the extension's official documentation for information on how to install it.