Is here are your keys a complete sentence?

No, "Here are your keys" is not a complete sentence. It is missing a subject.

A complete sentence needs a subject (who or what is doing the action) and a verb (the action).

Here's how you could make it a complete sentence:

* "I here are your keys."

* "Here are your keys." (This uses the implied subject "you")

Let me know if you'd like to see more examples!