alt Hacker NewsHardly matters, this isn't a problem that you'd have these days with modern LLMs.
Also, a model can always use a proxy to turn your tool calls into XML
And feed you back json right away and you wouldn't even know if any transformation did take place.
We do see fewer invalid JSONs on latest bigger LLMs but still can happen on smaller and cheaper models. There is also case when input is truncated or a required field not found, which are inherently difficult.
On XML vs JSON, I think the goal here is to generate typed output where JSON with zod shines - for example the result can type check and be inserted to database typed columns later