Segments

Every segment for one app — rules, a human-readable rendering of them, and a live subscription count evaluated at request time, so a large app pays for that count on every call. The default target segment sorts first.

The response also carries the field catalogue (fields): the filterable fields, their operators and hints, which is what a rule builder needs.

Creates a segment from a name and a rule list. Rules are compiled before anything is written, so a malformed rule is a 400 naming the problem rather than a segment that silently matches everything.

Setting is_target_default: true moves the default off whichever segment currently holds it — there is exactly one default target per app.

Deletes a segment. Managed segments cannot be deleted — the built-in ones an app is created with are a 409.

If the deleted segment held the default target, the default falls back to Total Subscriptions, or to the oldest remaining segment, so an app is never left without one.

Updates a segment's name, status (Active or Paused), rules, or its default-target flag. Replacement rules are compiled before they are stored.

The default target can only be moved, never cleared: is_target_default: false is a 400 telling you to make another segment the default instead. A patch that changes nothing is also a 400.