Some functionalities of the drivers and Mongo Shell require access to information on the shared collections. Such information is persisted in the config database owned by the Config Server. 

Commands, like db.collection.getShardDistribution(), are currently implemented by accessing directly to these config collections, which requires to be aware of implementation details that could change from one version to another of the server.

The idea is to decouple these command implementations from the internal representation of the system collections by exposing a programmatic API. Such API can be used to retrieve information on sharded collections, ensuring support and consistency regardless the internal representation of this information.