Authentication
Turning a client id and secret into a one-hour access token.
This is the only unauthenticated endpoint in the API, and the only one
that reads your client secret. Cache the token you get back and re-request
it when it expires or when a call answers 401.
If the account restricts access by IP (Settings → Security & login), that restriction is enforced here as well — a call from an address that is not on the list is refused before any token is issued.
Get an access token
Exchange a client id and secret for a bearer token that lasts one hour.
Inspect the current token
What this token can do: which account it belongs to and exactly which scopes it