What’s wrong with this sentence, “He will be here on us embassy courtesy visit and so I have no clues about his schedule”?

Since it appears that you are speaking of someone who will be the guest of the U. S. Embassy, the wording should be more formal depending on the person or people to whom the message is directed. Consider: He will be here at the U.S. Embassy on a/paying us a courtesy visit. Consequently, I do not know what his schedule will be. I’m not sure if you want to use ‘consequently’. Personally, I don’t understand the relation between a courtesy visit and not having information concerning a schedule. Perhaps those with whom you correspond understand this since it may be something typical. However, if this is not the case, I would use ‘unfortunately’ rather than ‘consequently’.