What word best describes the actions of the house in "There Will Come Soft Rains?"
Probably the most appropriate word to describe the actions of the house is "mechanical." The advanced technology of the house was meant to make the house more "alive" and able to provide for the human inhabitants in making their lives more convenient. In the story, the house is described with vibrant terms and it is often personified. This is done to illustrate the irony that it is in fact not alive.
Advanced technology can improve human life but it can also have a dangerous side (as it did in this story). When the story begins, an atomic explosion has already occurred. There are no humans left in the house and probably in the immediate area. All that's left is the computerized house that speaks, sings, feeds, and shelters the family who is no longer alive to enjoy it. The house is continually personified but it really continues to behave like a machine. Since the house is a computer, it continues to function according to its programming, unaware that the family it "cared" for is now gone. Note the first line of the story. The house is personified but only because it is programmed "as if" it were alive and sentient:
In the living room the voice-clock sang, Tick-tock, seven o'clock, time to get up, time to get up, seven o'clock! as if it were afraid that nobody would.
This story is a cautionary tale about the dangers of technology. Bradbury was not against technology. He merely recognized the inherent dangers; not just with atomic weapons but also with things (such as the house) that detract from the human experience. The more the house does for the family, the less the family has to do for themselves. In this respect, another appropriate word for the house (at least when the family was still alive) would be "lulling" or maybe even something like "soul-stealing" since the house, in doing more than the family, becomes more alive than the family itself. But after the family is gone and the house continues to administer to them, one could also say the house is "unaware" or "unconscious," something to emphasize the fact that the house is only seemingly, but not actually, alive. This is interesting because the house is sort of the main "character" in the story.