When I build a RESTful API, I use an MVC pattern. And in order to make controllers skinny and code reusable outside of the API (e.g. in Cron tasks), I put much of my code into services (commonly known as libraries).
My routers delegate to controllers which then delegate to services, which use models.
I am wondering: Does it make sense for services to use models? So
router > controller > services > models
Or, should models use services? So
router > controller > models > services