worldcat discovery versus metadata apis

From: Eric Lease Morgan <emorgan_at_nyob> Date: Tue, 22 Mar 2016 12:15:41 +0100 To: CODE4LIB_at_LISTSERV.ND.EDU

I’m curious. What is the difference between the WorldCat Discovery and WorldCat Metadata APIs? 

Given an OCLC number, I want to programmatically search WorldCat and get in return a full bibliographic record compete with authoritative subject headings and names. Which API should I be using?

—
Eric Morgan