I also released a hosted version of my open-source libraries ReLLM and ParserLLM that already supports APIs for

* Regex completion for LLMs

* Context-free Grammar completion for LLMs

https://thiggle.com/

[0] https://github.com/r2d4/rellm

[1] https://github.com/r2d4/parserllm

[2] https://github.com/thiggle/api

There's also another API on Thiggle that I've build that supports classification via a similar logit-based strategy.