A downhole tool has a housing with a communication path extending from a first to a second part of a bore. An indexer disposed in the communication path is movably responsive to applied pressure at the first part. The indexer counts a number of applications of the applied pressure and permits fluid communication of the applied pressure from the first part to the second part in response to the counted number. An insert in the housing bore sealably encloses the second part of the communication path and is movable from a first position covering to a second position uncovering a port in the housing. At least a portion of the insert acted upon by the applied fluid pressure in the second part initiates movement of the insert from the first to the second position. A kit having a modular housing portion and the indexer can adapt the downhole tool for use.