How to specify object type for Code templates?

If you want the rule editor to be able to get a drop down of properties to choose from, you would want to use a Class Property Provider.  It is on the SRL tab of the providers in the upper left hand corner.  You would choose the Claim class, and then there are additional configuration choices you have, such as to focus on a specific type of properties, or to filter out properties you do not want to show.  Then once you have configured it, you can click on the Use Default Generation drop down to make sure the properties you want will be the ones showing up.

If you are only asking about the code completion capabilities, from my testing, they only seem to work if "theClaim" is a global variable.  For a code template, you frequently don't have the context of the full ruleset or function where the object gets defined, so often code completion would not be able to determine the class of the object you are referencing.