What problems solace solves when I use an Async API

@rramakrishnan if you are referring to APIs as REST APIs then you will need to use OpenAPI spec to define your REST based APIs. Basically think of AsyncAPI to event APIs what OpenAPI is to REST APIs. So if your microservice publishes key domain events you can use AsyncAPI to define those events. As what Himanshu mentioned, the key concept with AsyncAPI is to capture how application is publishing/consuming events.