The sentence
東京へなにしに行くの?
translates to
What are you going to Tokyo for?
Question: How do we parse (and what is the meaning of) にしに行く? (I'm assuming なに is just 何).
Attempt: According to this question, the term "なにしに" is short for
何をしに来たんだ?
but that seems to collide with with なに and 行く already in the sentence?