Apples' Sandobox is supposed to use Apple Event Access Groups, which allow applications to communicate with each other, as described in the WWDC video "Session 206 Secure Automation Techniques In OS X"
However, what is not mentioned (and I could find no reference to it in Xcode 5.x documentation) is how can I find out which Apple Event Access Groups are defined for a specific application.
For example, if I want my App to communicate with Pages (or Photoshop, or Firefox, etc.), how can I find documentation about its Apple Event Access Groups? Where are they defined, and what tool can I use to find them?
Apple Events from sandboxed apps is typically done with Apple Script. There is documentation for the entitlement needed here:
To find which app provides access groups is a bit of a hassle and there aren't many available. Use terminal and sdef to find out. this will give you an XML which you can read and look for access-group
eg in Console:
sdef /Applications/Mail.app > mail.sdef.xml
open mail.sdef.xml
Then you'll see the line
<access-group identifier="com.apple.mail.compose" access="rw"/>