That is a dilemma! Perhaps you can introduce the summary with a little background on Frost's circumstances for writing this poem and then do your synopsis.
Your response should take the best part of a page. Always read poetry out loud; notice images and rhymes or rhythms that appeal to you. Phrasing and word choice also elicit responses as does metaphors and other literary devices. In a response, for example, you can write about how you like the image of ice paired with that of fire because.....The use of the word suffice certainly is an understatement. What is your reaction to this?