I am really surprised OpenAI didn't think about this and deliberately try to make these plugins not work with third party engines.
For example, they could have required the schema file be uploaded to them in your account. That way the majority of plugins wouldn't have publically accessible schemas.
Author here. It's such early days in this space and things are evolving quickly -- OpenAI's plugins system is also still in Alpha. We think it's a good time to have a conversation and ideally build an open plugin protocol that everyone can benefit from. It will help unlock even more innovation in this space. We have seen this in the evolution of language servers after Language Server Protocol, and how that benefited so many more developers and gave us better IDEs.
For example, they could have required the schema file be uploaded to them in your account. That way the majority of plugins wouldn't have publically accessible schemas.