A phrase cannot be used as a stand-alone utterance, e.g. "reading a book" is a phrase. However, with proper intonation etc., it can become a sentence, ("What are you doing"?) "Reading a book."
If the phrase is clear in context can it stand alone and stand as a sentence?
*a gift for doing all the work.
a story with great power.
a final conclusion to the trial.*
She was writing a story. A story with great power.
He took the money. A gift for doing all the work.
The case was closed: a final conclusion to the trial.