At the very least, you should make sure your logger can EXPORT an ADIF format file that our members can upload. Better yet is a real-time automated interface (see below).

• List of compatible loggers, user reviews, market share, etc. Make sure your logger is listed!
• Minimum acceptable ADIF log content specifications
• Real-time logger interface specs for uploading one or more ADIF records or an entire log file at the time the QSO is being conducted
• URL to obtain the date/time of last upload of logged-in user (you can specify Username(callsign), Password, and optionally a QTHNickname to find this information without logging in)
• Download what you uploaded (OutBox)
• Download incoming eQSLs in ADIF format (InBox)
• Verify an eQSL is valid
• Retrieve one eQSL graphic
• AG Member List is updated 6 times a day (currently 0300, 0700, 1100, 1500, 1900, 2300 UTC), this is a very long list of callsigns (ham or SWL) that have AG status (about 1Meg in size). You can load this into your own local database and update it every few days. (Note: As of 20Mar2024 1600UTC this no longer includes accounts autogenerated by LotW imports)
• AG Member List Dated is the same as AGMemberList.txt but contains the date of the last ADIF upload or import, separated by a comma from the callsign (about 2.5Meg in size). If no date, the date will be 0000-00-00. Unlike AGMemberList.txt, no SWLs are included in this file.
• Full Member List in CSV format (can be loaded into CALL3.TXT for WSJT-X lookups!), updated 4 times a day, with Grid Square, AG status flag, and date of last log update (about 6Meg in size) (this is experimental and subject to change until this comment is removed!) (Note: As of 21Mar2024 1600UTC this no longer includes accounts autogenerated by LotW imports)