There are a large number of companies that regulate the operation of SIM cards: ETSI, 3GPP, ISO... And it often happens that different companies define the same standards in different ways.
Card Application Toolkit is a set of commands with which the SIM card can communicate with the phone. For example, using the DISPLAY TEXT command, the SIM card can display information on the phone screen.
This is an incomplete list of standards that define the operation of the Card Application Toolkit:
ETSI TS 102 223
ETSI TS 131 111
3GPP TS 51.014
And each standard changes from year to year! What SIM toolkit standard do Android system developers follow?
I have studied developer.android.com but they don 't say anything about standards and versions