You can issue a command (such as
C-h k) that uses the minibuffer from the minibuffer itself only if you set
enable-recursive-minibuffers to non-
But most likely what you really want here is to get help on a minibuffer keymap. For that, use
C-h M-k (
describe-keymap) from library
There are a few minibuffer keymaps. You might need to check more than one with
C-h M-k, depending on which ones are being used for what you are interested in.
See the Elisp manual, nodes Completion Commands and Text from Minibuffer for descriptions of the minibuffer keymap variables.
For example, you might try
C-h M-k minibuffer-local-keymap.
On the other hand, if Helm uses its own keymaps in the minibuffer then you might need to enter the name of one of those when prompted by
Keep in mind also that a minor-mode keymap overrides the predefined minibuffer keymaps, which are local maps.
If you used Icicles (but Helm and Icicles are probably incompatible) then you can see which keys are available anytime, in any given context, including in the minibuffer.
If the minibuffer is active then
M-S-TAB at any point shows you the key completions. If no prefix key has been pressed yet then it shows you the top-level key bindings available in the minibuffer at that time. The key = command bindings are shown as completion candidates in buffer
*Completions*. You can filter them by key name or command name or both. And keys that are bound locally (i.e., in a local keymap) are highlighted specially.
If the minibuffer is not active then
S-TAB gives you the same behavior: it shows the available key completions at any time.
See Icicles - Key Completion.