Did you find it hard to create structured output while also trying to make it reason in the same prompt?
The second phase can be with a cheap model if you need it to be.
Pseudo-prompt:
Prompt 1: Do the thing, describe it in detail, end with a clear summary of your answer that includes ${THINGS_YOU_NEED_FOR_JSON}.
Prompt 2: A previous agent said ${CONTENT}, structure as JSON according to ${SCHEMA}.
Ideally you use a model in Prompt 2 that supports JSON schemas so you have 100% guarantee that what you get back parses. Otherwise you can implement it yourself by validating it locally and sending the errors back with a prompt to fix them.