This is an adapter add-on for the Mozilla WebThings Gateway that allows a user to discover native web things on their network.
If you're trying to MANUALLY add a server (e.g. if mDNS discovery isn't working) that contains multiple web things, i.e. the "multiple-things" examples from the webthing-python, webthing-node, or webthing-java libraries, you'll have to add them individually. You can do so by addressing them numerically, i.e. http://myserver.local:8888/0 and http://myserver.local:8888/1.