In March 2020, the service was discontinued.
MTDataAPIDebugger is Movable Type (Blogging Platform that provided by Six Apart, Ltd) Data API Client for Web developer.
It can post an entry, upload files, and get list entries, blogs and categories.
MTDataAPIDebugger can send custom GET/POST request (the authenticated request), view HTTP request header and request body, and response header and response body (it is JSON string).
JSONViewer can parsing JSON string. It would be useful to understand the data structure.