With D2L there are two ways that grade items can be associated with an LTI assessment. The first way is to associate a grade item (one that you create yourself) to an External Learning Tool Link. This approach certainly works, but it puts configuration effort on you. Alternatively, a grade item can be automatically created when the Tool Provider sends back the first grade for a user for the specific External Learning Tool link. The automatically generated grade item will be associated with the External Learning Tool Link in the context of the course. Students would have to launch through the assignment link once, so we may obtain the information required to send grades back.