I implemented a similar pattern in my LLM tool and Python library back in February: https://simonwillison.net/2025/Feb/28/llm-schemas/

My version works with Pydantic models or JSON schema in Python code, or with JSON schema or a weird DSL I invented on the command-line:

  curl https://news.ycombinator.com/ | \
    llm --schema-multi 'headline,url,votes int' \
    -m gpt-4.1 --system 'all links'