When I load Automator workflow into BTT it doesn't execute properly.

I have a shell script that takes the selected/highlighted word as input and inserts it into a file (via Python).
(workflow in Automator)

When I try to run it through BTT it just inserts a blank space. (BTT setup)

I also tried executing the shell script natively in BTT but it does the same thing.

Why is this?

So I guess this is happening because I need something to "grab" the selected text and pass it in BTT.

Conveniently there is a 'Save selected text to variable selected_text' that sounds like what I want.

Now I just want to use this variable in my shell script