Normally I'd put each `@!attribute` tag above the `attr_accessor` call as below so that YARD's 'Show Source' shows the call being documented.  (You also didn't add the r/w flags.)

```ruby
# @!attribute [rw] add_code
#   @return [String] The path to a shellcode file to execute in a separate thread.
attr_accessor :add_code

# @!attribute [rw] arch
#    @return [String] The CPU architecture to build the payload for
attr_accessor :arch
```