The API Docs contain the following information:
- Kintone REST API
Contains REST APIs for creating/retrieving/updating/deleting records and uploading/downloading files.
There are also APIs to retrieve general information about specific apps, and APIs to retrieve the form specifications of apps. - JavaScript API
Contains APIs for Kintone JavaScript customization. You can upload JavaScript codes to your Kintone apps, so they will run when the user is browsing Kintone.
There are list of Kintone events that you can use, along with API to retrieve record data, run Kintone REST APIs and run external APIs. - Plugin Docs
Contains APIs for creating your own Kintone Plug-ins.