message: Clarify components API doc
diff: @@ -3309,6 +3309,13 @@ null;
  Sent from the client to the server to get the list of component groups available
  in runtime.
  +The engine is started with an empty list of libraries loaded. It means that the
  +request should be sent after the first
  +[`executionContext/executionComplete`](#executioncontextexecutioncomplete)
  +notification indicating that all the libraries are loaded, and the component
  +group list is populated. If the request is sent before the first notification,
  +the response may be empty or not contain all available components.
  +
  - **Type:** Request
  - **Direction:** Client -> Server
  - **Connection:** Protocol
  