Tumblr has a sharer just like Facebook and Twitter, Tumblr's is: http://www.tumblr.com/share/. I believe that Tumblr's works by looking at the referring URL and uses that.
I cannot seem to find any documentation to override that. I want to pass in an additional key into the URL that is sent by default. Any ideas how to do this?
Tumblr share URL as of Aug. 2014:
http://www.tumblr.com/share/link?url=[uri encoded URL]&name=[title]&description=[description]