Developing the Firmware
The ESP RainMaker project is built on top of ESP IDF and provides C APIs for firmware development. The APIs have been designed such that developers will have to write only the application logic and leave the rest to the RainMaker framework. Detailed API reference can be found here.
Developing the Clients
There are many ways in which the clients can be developed for ESP RainMaker. You may use the raw REST APIs or any of the higher level client APIs.
The REST APIs can be used to build your own applications, similar to the phone apps and CLI already provided with ESP RainMaker.
Swagger documentation for these can be found here. You can even try out these APIs directly from Swagger. Please keep checking for updates and additional features.
The ESP RainMaker offers a python based CLI to try out all the User level functionality similar to the phone apps. It also has libraries which you can use in your own python scripts. The API reference for that can be found here.
Phone apps are available on the respective app stores for direct download and usage. The source code for these apps is available on GitHub.