Yes, PROMPTS is a Scrabble word!

Letter values in Scrabble US: P 3, R 1, O 1, M 3, P 3, T 1, S 1.

Is it a valid word?

PROMPTS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a cue given to a performer (usually the beginning of the next line to be spoken)
(computer science) a symbol that appears on the computer screen to indicate that the computer is ready to receive a command

give an incentive for action
serve as the inciting cause of
assist (somebody acting or reciting) by suggesting the next words of something forgotten or imperfectly learned

Also: command prompt.