WARNING: This page is about a different car, the 2016 BMW Z4, 2015 BMW Z4, and 2014 BMW Z4. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Crimping Tool (2327752)
Courtesy of BMW OF NORTH AMERICA, INC.
NOTE:
Basic pliers (e.g. in conjunction with die 54 0 230 for crimping the cables on the soft top in E93)