[nandemo]

For good hackers, it's a good sign if the company has high standards for hiring. But the candidate has to be already interested in your company for some other reasons.

If it's a cool company like (say) ITA or Atlassian, I'd be happy to take the time to solve a couple of puzzles and send my code if it got me an interview.

If it's a random startup, I would likely not bother wasting my time before an interview. At the very least I'd need a phone screen first.

In my opinion, the ad should give an idea that you're doing something exciting without sounding grandiose. It should give a good description of the position and responsibilities. You should avoid HR-speak and requirements that are too specific.

In any case, I think the key is not the job ad itself. Your company must be seen as a desirable workplace for good programmers. You need to market yourself for potential candidates, even before you start hiring.

Are you making an interesting product? Does your current team loves to work there? Do you have low turnover? Are you in good terms with people who left the company, and would they heartily recommend you? Etc.