How to apply a Clio task template to a matter through the API

There are two versions of this job and they have different answers. Most of the confusion, including ours, comes from assuming they are the same thing. Applying a whole template list to a matter Clio's interface has a button for this, and the natural assumption is that there is a matching endpoint on the task template resource. There is not. Nothing under /task_template_lists will assign anything to a matter, and no path in Clio's spec contains "apply". It is done from the matter instead. Both POST /matters.json and PATCH /matters/{id}.json accept a nested array: task_template_list_instances[] : task_template_list : { id } required on POST assignee_id : the user the list is assigned to notify_assignees : whether assignees get notified due_at : ISO-8601 date (format : date, not date-time) Those are the only two operations in the API that accept it. Note the asymmetry: on POST /matters.json the task_template_list object is required, and on PATCH /matters/{id}.json the item schema marks nothing as required at all. POST /task_template_lists/{id}/copy.json exists and sounds like the thing you want. It is not. It duplicates a list into another list , takes name , description and practice_area (all optional), and has no matter parameter. The two problems that will actually cost you time Instances are write-only. task_template_list_instances appears in those two request bodies and nowhere in the matter response schema. So there is no documented way to ask "does this matter already have the list on it?" You verify by fetching /tasks.json filtered to the matter and matching on names, which is uglier than it sounds and is most of the reconciliation work. Which makes idempotency your problem. If your automation fires the PATCH twice, nothing in the API stops you assigning the checklist twice. For anything triggered off matter creation or a stage change, decide up front how you detect an already-applied list, because the readback above is the only tool you have. Between them, th