That depends upon a lot of things. And, it's really quite possible that
you're not.
Information is intangible. You cannot use code that is copyrighted because
it's protected by copyright. And, you cannot write your own code to
implement an algorithm that's protected by a patent.
But "trade secrets" have no protection whatsoever once they've been exposed.
That's why you're forced to sign NDAs before you're made privy to trade
secrets. There is no legal protection for the secret itself, so the NDA
becomes the sole legal recourse of the party with the trade secret.
The issue is an unpublished API. It could copyrighted but that doesn't mean
that you can't read it. And, the copyright only has teeth with respect to
the reproduction of the document. It CANNOT DICTATE WHAT YOU DO WITH THE
INFORMATION THAT YOU HAVE LEARNED BY READING THE DOCUMENT.
I'm not a lawyer, but I've seen lawyers discussing this stuff...
Stig