More in-depth documentation will be forth coming.
However the quick overview is HamDB.org offers access to it's database using a very simple REST API.
It can be accessed using a HTTP GET request to the URL http://api.hamdb.org/CALLSIGN/FORMAT/APPNAME
CALLSIGN should be the requested amateur radio callsign
FORMAT should be one of the supported formats you'd like the data returned in (xml, json, csv)
APPNAME should be a string that identifies your app or project
If the callsign is not found within the HamDB.org database, a result will be returned in messages -> status value of NOT_FOUND
Any questions, comments, or suggestions, please reach out. I can be reached on twitter @kk6nlw or at kk6nlw [at] gmail