Capture funds reserved for a Purchase (status == hold). You can place a hold (authenticate the payment) using skip_capture == true when creating the Purchase and ensuring your client submits the payment form.
If this operation takes too long to be processed on the acquirer side - you will get a response with status code 200 and a Purchase object having status = pending_capture in body (you will receive a corresponding Webhook callback too for a purchase.pending_capture event). To be notified of a successful operation completion, please subscribe to purchase.captured callback event - it will deliver an updated Purchase with status = paid.
If capture fails due to payment processing error, you will receive HTTP response code 400 with error code purchase_capture_error. In this case, to get more details about the error, you should perform a GET /purchase/ request for the Purchase you tried to capture. In transaction_data.attempts array (newest element first) you'll find the corresponding attempt with error code and description in .error parameter. By default the full amount is captured, the amount body param is optional.
Click Try It! to start a request and see the response here!