why not generate the API?

[casualjim]

There is manual handling of arguments and then generating a swagger spec from what you have.
There is another way to leverage swagger which is by generating a server based on the spec. This gets quite a lot of usage so should be fairly stable.
It makes your swagger specification the contract for your service and removes busy-work because that code is particularly boring to write and you're not actually doing anything innovative with it.

I'm always available on slack if you want to discuss further