Finding out if any clips on a layer are connected requires downloading the full status of every clip on the layer with /composition/layer/1 which is a) huge and b) slow.
A new api call would allow get and post for the current connected clip on a layer:
GET,POST /composition/layer/1/clips/connected
GET,POST /composition/layer-by-id/abc123/clips/connected
In my use case I'm populating a layer from a folder of files. I want to know if any clip is connected so that I can reconnect it when the import is complete.