gistfile1.txt

on replace_chars(this_text, search_string, replacement_string)
  set AppleScript's text item delimiters to the search_string
  set the item_list to every text item of this_text
  set AppleScript's text item delimiters to the replacement_string
  set this_text to the item_list as string
  set AppleScript's text item delimiters to ""
  return this_text 
end replace_chars

tell application "Google Chrome"

    set theName to name of active tab of front window
    set theURL to URL of active tab of front window
    set theURL to my replace_chars(theURL, "%", "%%%")

    return "[ %| ](" & theURL & ")"

end tell