How do you generate OpenAPI JSON definition?

I plan to connect to several different 3rd party API’s. Many do not provide JSON definition files which would make things much easier.

Are there any automated tools that could perhaps scan a 3rd party API and generate that file? How did dreamfactory create these 3rd party definition files?

Also, the terminology is kind of confusing. It seems there are several definitions of a JSON definition file. Dreamfactory calls them service definitions.

Bit of an update. There is a 3rd party repository of openapi definitions that has been collected. Some but not all of the 3rd party API’s I plan to use are in there. I tried to put a couple of them into dreamfactory service definition. Seems to more or less work based on limited testing.