I know if you do the autocompletion you can view the description of the function you are selecting...
Is there any way to view the description in the same way but without autocompleting, just selecting the function over the cursor position?
That preview window is populated by Eclim (using Eclipse) on the fly during completion but Eclim doesn't provide any user-level command to get that info outside of the context of completion.
In order to show the signature of the function under the cursor:
<C-w>}
opens the tag under your cursor in the preview window:ptag foo
tag foo
in the preview windowThis feature depend on the availability of a tags
file.
See :help preview-window
and :help tag-preview
for some related commands.