In Thor: Ragnarok movie, Doctor Strange consulted a book to check if the portal spell required any Asgardian modification. Why didn't he also check for Jotun modification as Loki is actually a frost giant from Jotunheim, not Asgardian?
The script (and movie) show that he was only studying the book of magic for a few seconds. One assumes that it simply said that it works for everyone, regardless of their planet of origin.
[Strange stands up and suddenly they are standing by a bookcase. Strange takes down an ancient book, flips through it.]
STRANGE: I’m just seeing whether this incantation requires any Asgardian modifications.
[Thor reaches out to the bookcase to steady himself.]
STRANGE (CONT’D): Nope.
Additionally, it's not clear whether Doctor Strange (a human from Earth) would have been aware that Loki isn't a full Asgardian. Although it's common knowledge to us, the audience, this factoid may have passed Strange by.