We use Open API specifications (OAS) for HTTP APIs. We use these in our microservice/applications to generate a Swagger UI, but it's also great for documentation and collaboration.
Some internal messaging is also done asynchronously via a message broker (RabbitMQ/AMQP). Is there something that other people/companies use to document async messages operations? It would be nice to just hand integration teams something like an OAS...
I'm currently working with a team who are evaluating Async API for describing services that use messaging over AMQP and other similar protocols. It sounds like it might address some of your needs?