It's unclear whether Pinterest took down its API documentation or whether pretty URLs are to blame. Either way, for now the Pinterest API, which had not been officially released, is again undocumented. The endpoint still appears active, as long as you are making public calls that don't require user authentication.
Update: The Pinterest API page now returns a 404. The company is now appears to be purposely pulling back its documentation.
That's the page that used to be Pinterest API documentation. There's now a user named "developers" with a board named "api." Because usernames are added to the URL, that profile page overrides what was there before. Apparently Pinterest hadn't reserved that username.
It's possible that Pinterest itself created the account to make its un-launched API documentation go away, but that doesn't seem likely. The company would be able to make the page go away in a number of other ways. It appears nobody is in too much of a hurry to replace the page, since it is unsupported publicly at this time.
For developers still looking for the details of how to use it, there's a cached copy on BOLT.
Currently the Pinterest API that is available is read-only. Attempting to use the OAuth endpoint to authenticate results in a 404 error.
Via Marc Mezzacca