Since 2016.01, Aimeos contains a JSON API modeled after the guidelines of http://jsonapi.org/. It allows full access to all shop data and is especially useful to manage the content.
Because you have access to all shop content, the JSON API is and should always be protected. The easiest setup is a HTTP basic authentication using an user name and password. Different authentication options are possible and it depends on the host application how the JSON API is protected.
There's also no common entry point to access the JSON API. This also depends on the host application and you have to retrieve the initial base URL from a configuration setting. Also the resource URLs are different depending on the environment but you can get the available ones by querying the meta data from the base URL (via the HTTP OPTIONS method).
When you've managed to authenticate your client and got the base URL from the configuration settings, you can start working with the Aimeos JSON API: