A downhole tool responsive to passage of one or more objects and applied fluid pressure, the tool comprising: a housing defining a housing bore therethrough and defining at least one port communicating the housing bore outside the housing; a plugless valve disposed in the housing and operable from an unobstructed condition unobstructing the housing bore to an obstructed condition obstructing the housing bore to the applied fluid pressure, wherein the plugless valve comprises a first insert and a valve element, the first insert disposed in the housing bore and defining a bore therethrough, the valve element disposed relative to the first insert and movable from an unobstructed condition unobstructing the bore to an obstructed condition obstructing the bore to the applied fluid pressure, the valve element in the obstructed condition permitting axial movement of the first insert in the housing bore from a closed condition covering the at least one port to an opened condition exposing the at least one port; and an indexer disposed relative to the plugless valve, the indexer configured to count the passage of a number of the one or more objects through the housing bore and to permit operation of the valve element and the plugless valve from the unobstructed condition to the obstructed condition in response to the counted number, wherein, in response to the applied fluid pressure against the valve element in the obstructed condition, the first insert is axially movable in the housing bore from the closed condition to the opened condition, and wherein the tool is configured such that applied fluid pressure in the housing bore obstructed by the valve element of the plugless valve in the obstructed condition communicates from the housing bore outside the housing via the at least one port. a housing defining a housing bore therethrough and defining at least one port communicating the housing bore outside the housing; a plugless valve disposed in the housing and operable from an unobstructed condition unobstructing the housing bore to an obstructed condition obstructing the housing bore to the applied fluid pressure, wherein the plugless valve comprises a first insert and a valve element, the first insert disposed in the housing bore and defining a bore therethrough, the valve element disposed relative to the first insert and movable from an unobstructed condition unobstructing the bore to an obstructed condition obstructing the bore to the applied fluid pressure, the valve element in the obstructed condition permitting axial movement of the first insert in the housing bore from a closed condition covering the at least one port to an opened condition exposing the at least one port; and an indexer disposed relative to the plugless valve, the indexer configured to count the passage of a number of the one or more objects through the housing bore and to permit operation of the valve element and the plugless valve from the unobstructed condition to the obstructed condition in response to the counted number, wherein, in response to the applied fluid pressure against the valve element in the obstructed condition, the first insert is axially movable in the housing bore from the closed condition to the opened condition, and wherein the tool is configured such that applied fluid pressure in the housing bore obstructed by the valve element of the plugless valve in the obstructed condition communicates from the housing bore outside the housing via the at least one port.