Depends to be honest. Where they expose OpenAPI docs it's dead simple to generate the models from that. In .NET I use those plus Refit and boom. Now I have full control and it took barely any time.
I like this approach too, but a non trivial amount of time the models come out wrong. I assume this is because of bad openapi docs, but maybe I'm wrong.
What do you use to consume the openapi docs and generate models with?
Haha yes we got bitten by that on a recent project but it resulted in a minor bug we patched pretty quick. I don't mind taking that downside.
Can't remember the exact name of it but it's one of the open API generators that supports all the major languages. Unfortunately the csharp and dotnet core generator generates clients with RestSharp which doesn't use the almighty HttpClient, so I consider them unusable, but it generates the models faithfully. If it so happens the open API spec is wrong that's unfortunate. Though usually if they have an SDK I just use the models directly from the SDK! That's the absolute sweet spot for me. Especially if their SDK is generated off open API it probably stays perfectly or acceptably accurate with incentives to correct any inaccuracies.
What do you use to consume the openapi docs and generate models with?