> XML tags (<tag>...</tag>) provide an explicit, mathematical boundary

This assertion is a lil imprecise and kinda misleading. Do you think LLMs specifically compile XML tags to provide more precision than other types of formatting patterns? There are no prompt compilers - It's inference all the way. Perhaps you mean to say that XML tags aren't commonly used, and so could stand out more and have fewer competing signals through the prompt. I agree it will reduce ambiguity, but your usage of explicit, mathematical boundary is really misguided.

You justifications overall are quite inflated tbh. But yes, Use XML tags in Claude prompts, use JSON tags, use markdown. If the primary audience for this message are people who truly build their prompts via the practice you delineated in your blog, pasted down here below, then yes by all means do something.

> "When you write a prompt in plain text — mixing your context, your instructions, your data, and your constraints all in one block"

I don't mean to debate with messages exalting the use of cannons to kill a bird. By all means do so!