End effectors with redundant closing mechanisms, and related tools and methods are disclosed. The disclosed end effectors may be particularly beneficial when used for minimally invasive surgery. An example surgical tool comprises an elongate shaft having a proximal end and a distal end, a tool body disposed at the distal end of the shaft, a jaw movable relative to the tool body between a clamped configuration and an open configuration, a first actuation mechanism coupled with the jaw and operable to vary the position of the jaw relative to the tool body between the clamped configuration and the open configuration, and a second actuation mechanism coupled with the jaw. The second actuation mechanism has a first configuration where the jaw is held in the clamped configuration and a second configuration where the position of the jaw relative to the tool body is unconstrained by the second actuation mechanism.