Now that is an interesting question!

Late and inexpert but I think that's a functional question. Does the prompt function as parol evidence or... Hm. If the prompt was not the product of discussion between the parties, but the product of only one party, then maybe? Maybe especially if it introduces ambiguities? Like contra proferentem?

Probably only if both sides were involved in writing the prompt. If only one side knows the prompt, it would not be evidence of the mutual intent of the parties.