Lately, I've been pondering about this question.
First of all, we already know that dialogue tags consist of a noun or a pronoun followed by a verb like "said," and "ask."
"Like this one," I said.
Also, when using an action tag, the dialogue must have a full stop.
"Like this?" I looked at the text above.
Would "is my only answer" be considered a dialogue tag with that structure? I can't really consider it one since it doesn't have the same structure.
"I don't know," is my only answer.