I’ve just posted a script to the Drafts Action Directory. It is a simple script to take the URL copied from Safari, and create a Markdown link to it.

There are two ways you can use it:

1. Press the button with no text selected.
   You end up with something like [|](url_copied) with the cursor between the square brackets (indicated with the character | in this example)
2. Press the button after selecting some text
   You end up with something like
   [this is the text I selected](url_copied)

In case you want to manually copy/paste the script into Drafts, here is the simple code:

// Create Markdown link 
var sel = getSelectedText();
var selRange = getSelectedRange();
var clip = getClipboard();
if (!sel || sel.length == 0) {
   setSelectedText("[](" + clip + ")");
   setSelectedRange(selRange[0]+1,0);
}
else {
   setSelectedText("["+sel+"]("+clip+")");
   setSelectedRange(selRange[0]+selRange[1]+3,0);
} 

This is by no means rocket science. I simply took the existing Markdown Link keyboard extension and added a variable that stores the clipboard content through the getClipboard() function.