Nobody in the original post or this entire discussion said anything about OpenAI until your comment.
I thought it was fairly obvious that we were talking about a local LLM agent... if DataHerald is a wrapper around only OpenAI, and no other options, then that seems unfortunate.
The agent is LLM agnostic and you can use it with OpenAI or self-hosted LLMs. For self hosted LLM we have benchmarked performance with Mixtral for tool selection and CodeLlama for code generation.