The words that represent verbs that would be useful in describing the purpose for a text are the following ones: Inform and define.
Cambridge dictionary defines the verbs "to inform" as "to tell someone about particular facts" and "to define" as "to say what the meaning of something is". When you are about to describe the purpose of a text, you are to inform the reader what you want to say and why you are saying it. You are giving meaning to your piece of writing.
