How do you consume OpenAPI 3.0 specifications?

As a member of this community, you might using OpenAPI specifications to define REST-like APIs to services. Or you might be a developer consuming an OpenAPI specification that you've been given. In some cases such APIs may simply be internal APIs used within an enterprise, while in other cases they may be exposed more openly to external developers.

Whichever role you are in, my question is about how the OpenAPI specifications are used by consumers of the API, especially when such consumers are outside of the API-defining organization. Do consumers typically just use them as a form of documentation and then develop clients by hand? Or is there an attempt to generate client-side code that meshes with the client application? Are existing tools sufficient to generate this code or are customizations to the tools needed? Or have home-grown tools have been developed? Does this include both client-side code for invoking the service and client-side type definitions (and the associated marshalling to and from JSON)? Does the choice of client side language (Java, C#, JavaScript, etc.) impact these decisions?

Thanks