This paper presents a method for determining sensing requirements for robotic assemblies from a geometrical analysis of critical contact-state transitions produced among mating parts during the execution of nominal assembly plans. The goal is to support the reduction of real-life uncertainty through the recognition of assembly tasks that require force and visual feedback operations. The assembly tasks are decomposed into assembly skill primitives based on transitions described on a taxonomy of contact relations. Force feedback operations are described as a set of force compliance skills which are systematically associated to the assembly skill primitives. To determine the visual feedback operations and the type of visual information needed, a backward propagation process of geometrical constraints is used. This process defines new visual feedback requirements for the tasks from the discovery of direct, and indirect, insertion and contact dependencies among the mating parts. A computational implementation of the method was developed and validated with test cases containing assembly tasks including all the combinations of sensing requirements. The program behave as expected in every case.