A message contains… now takes Any of these words: type a word and press Enter or a comma, and it becomes a chip. Any one of the words starts the automation, so one automation covers every word people use for the same thing — up to 20 words, each up to 40 characters.
A word is found at the start of a word in the message: “book” finds “Booking” and “#book”, never “Facebook”. Capital letters and accents don’t matter. Someone comments on a post uses the same rule for its words.
On the web and in the app. Guide: «Reply automatically when a message contains a word».