Is this a part of a stable api? Can I use it in an app to consume the data?
https://docs.google.com/spreadsheets/d/<KEY>/export?gid=<WORKBOOK_ID>&format=csv
AFAIK https://docs.google.com/spreadsheets/d/<KEY>/export?gid=<WORKBOOK_ID>&format=csv
is not part of a current API.
The Google Sheets API documentation link is