It's not recommended to poll position APIs to fetch last_price; it gets updated arbitrarily with a slight delay. It is thus not possible to provide accurate, real-time P&L with an HTTP response, and the recommended way is to use WebSockets/quotes and consume real-time data and compute P&L.
and why is something like this not clearly documented?
i am not looking for real time but i need some idea how much the delay can be.