Contract first development - the event driven way!
Contract first application development is not limited to synchronized RESTFul API calls. With the adoption of event driven architecture, more developers are demanding a way to set up contracts between these asynchronous event publishers and consumers.. Sharing what data format that each subscriber is consuming, what data format is used from the event publisher, in a way OpenAPI standards is going to be very helpful.
But in the asynchronous world, it is ever more complex, not only do you need to be caring about the data schema, there are different protocols, serializing, deserializing mechanisms, and various support libraries. In fact there are talks on AsyncAPI.