The information from the parameter auto_renew with the values true or false is available when you call the endpoint publisher/subscription/list and pass the subscription_id into the q parameter.
A sample request for US Production would look like this:
https://api.piano.io/api/v3/publisher/subscription/list?api_token=<api_token>&aid=<aid>&q=RCI5TSQDEABC&offset=0&limit=10
All available base URLs for Production are listed here.
And the response would contain the information about the state of the subscription's auto-renewal:
"subscriptions" : {
"subscription_id" : "RCI5TSQDEABC",
"auto_renew" : false,
"next_bill_date" : 1609254620,
"payment_method" : "Visa ending in 1111",
"user_payment_info_id" : "PMF0ZZ481234",
"upi_ext_customer_id" : "123",
"upi_ext_customer_id_label" : "Payment provider ID",
"billing_plan" : "$9.99 per month / free trial for 1 week",
"end_date" : 1609234981,
"cancelable" : false,
"cancelable_and_refundadle" : false,
"status" : "expired",
"status_name" : "Expired",
"status_name_in_reports" : "expired",
}