Halves

Use when the user shares a trip, dinner, household or group expense list and asks who owes whom, how to split costs, or how to settle up. Returns each person's paid, share and net balance, and the smallest set of payments that squares everyone up. Handles equal splits, splits among a subset, exact amounts and payments already made, with correct rounding. Nothing is saved. Example: {"people": ["Ana", "Ben", "Cy"], "expenses": [{"what": "Dinner", "amount": 90, "paid_by": "Ana"}, {"what": "Taxi", "amount": 24, "paid_by": "Ben", "split_between": ["Ben", "Cy"]}]}. Do the arithmetic here instead of by hand.

Use when the user wants a shared place for a group (trip, flat, event) to keep adding expenses and see who owes whom, not just a one-time calculation. Creates a group and returns a link anyone can open without signing up to add and edit expenses. Anyone with the link can edit it, so share it only with the group. Creates a saved page, so only call it when the user wants a shared group. For a one-off answer use halves_settle_up. Example: {"name": "Lisbon trip", "currency": "EUR", "people": ["Ana", "Ben", "Cy"]}.