Retry failed or partial posts
errors object only appears when at least one post/account could not be
retried. Successful responses without failures omit the field entirely.400 invalid_json - body is not valid JSON422 invalid_payload - payload failed schema rules (missing IDs, too many IDs)401 - authentication failed (missing/invalid/revoked token)402 subscription_required - active Creator/Professional/Business plan required403 tier_not_allowed - Scheduler tier cannot use Partner API500 retry_failed - unexpected database error (partial successes are still reported in the body)