Question
What is the “dress code” of formal Jewish Prayer (like the shemoneh esrei)?
Answer
Thanks for asking this question. The code of Jewish law tells us that, for prayer, we should dress for the occasion of speaking to the King of kings. That means to be as respectfully attired as you would be when visiting a mortal monarch. Practically, I would recommend that you discuss this matter with a trustworthy Rabbi in order to best implement this requirement. However, one certainly needs to be dressed with at least a shirt and appropriate pants / skirt. Also, one should not pray barefoot, and men should have a head covering.
Pray well!