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 contents
• 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 info and hyperlink to the list. Updated several times a day, this is a very long list of callsigns that have AG status. You can load this into your own local database and update it every few days..
• If you want to write code to retrieve a particular eQSL, contact N5UP at eQSL.cc (we don't publish this information to the general public, to avoid hacking attempts)