The COUNTER 5 Title Master Report and Platform Master Report and their Standard Views are available for SpringerLink and nature.com activity from January 2019 onwards. The Database Master Report will be available in 2021. Our plan is to not supply Item Master Reports..
Springer Nature Librarian Portal: CSV and TSV; Via SUSHI: JSON.
There are no limitations. Be aware though, that the files can get quite big if you add several months.