Note: In this and other examples, we use :id (or :something) in the request URLs as a placeholder, and you should substitute values specific to your data (your workspace ID, the ID of one of your tasks, etc).
The contents of a workspace are organized in a tree. Every workspace has a root. The root may be empty (in which case you have an empty workspace), or it may contain projects and packages. In turn, these projects and packages may contain other items.
To fetch only the root, request treeitems with a depth of 0:
% curl https://app.liquidplanner.com/api/workspaces/:id/treeitems?depth=0
... wall of text ...
If you want the entire tree, you do:
% curl https://app.liquidplanner.com/api/workspaces/:id/treeitems?depth=-1&leaves=true
... larger wall of text ...
See The Workspace Tree for details.