In this sentence from the "Who is she?" lesson: 你必须得告诉我?, what is the purpose of “得“ ? It seems confusing and unnecessary. Doesn't the sentence mean the same thing without it?

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in this sentence from the “Who is she?” lesson: 你必须得告诉我?, what is the purpose of “得“ ? It seems confusing and unnecessary. Doesn’t the sentence mean the same thing without it?