[NitpickLawyer]

It's a tradeoff between getting "good enough" performance w/ guided/constrained generation and using 2x calls to do the same task. Sometimes it works, sometimes it's better to have a separate model. One good case of 2 calls is the "code merging" thing, where you "chat" with a model giving it a source file + some instruction, and if it replies with something like ... //unchanged code here ... some new code ... //the rest stays the same, then you can use a code merging model to apply the changes. But that's become somewhat obsolete by the new "agentic" capabilities where models learn how to diff files directly.

[BoredPositron]

Haiku is my favorite model for the second pass. It's small cheap and usually gets it right. If I see hallucinations they are mostly from the base model in the first pass.

[hedgehog]

Depending on the task you can often get it in about one request on average. Ask for the output in Markdown with reasoning up front and the structured output in a code block at the end, then extract and parse that bit in code.