Sending a message into a Livechat

Hello guys,

I am currently working on integrating a chatbot (external one) into the live chat feature. This means users of my website will be able to open up the chat window in the lower right corner (standard configuration) and create a new livechat room.

My software detects a new room by calling “/livechat/rooms” but sending an actual message doesn’t seem to work?
This feature doesn’t need auth so it is surely not meant for my atuhenticated bot-user to be used - rather than by the users of my site?
This feature works great for posting into channels, but I don’t get the extra line in the documentation about “channel” AND “roomId” being required? you can send a request without the roomId and my tests ended up in failure when I tried to add the roomId param to my JSON call …

So, how would one send a message into a livechat room via REST API?