Why Mercury ?
First of all, the name Mercury was given keeping in mind the first planet of our solar system, which is the minor one and also the fastest in his orbit around the Sun, and in the same way, Mercury is a software piece which is little in size, but able to be put to work - and do what is it purposes - really fast.
Second, Mercury was created from the idea that we are in XXI century, and with the current technologies available, there is no more reason to spend time to write code to deal with single CRUD tasks. There are several frameworks and micro-frameworks existing in the market which support REST services building but, all of them requires some coding to deal with CRUD operations - basically, at least define the model, write the controller with all operations/methods needed, and after that write the router configuration to the corresponding services.
What was in mind when creating Mercury, as said by the CCR concept presented before, was to build something which doesn´t need coding to do these repetitive tasks, you can connect it to your database(s), configure your models - according to the tables and views available in the configured database(s), configure the routes, and all needed REST services will be available, and of course, if there is some need to write more specific REST services - like build complex report data combining several models data, or merge your models data with external services, like geocoding, for a little example - provide the ways to do that with ease - without need to write any SQL code, keeping the standards. This is the general spirit, go ahead to know a little bit more about the mechanics behind it.