Yes, I am familiar with OpenAPI generators including this one but I have not used so far.

But to use these generators we need to first build OpenAPI specs which includes not only API end points but also JSON schema for our entities (invoices, orders, gl, vendors, customers etc.)

If there is no hurry, we can go to this route.

If we need something ready today then existing API is ready and can be implemented after your testing. I just need to add authentication to it.

Regards