The idea itself is sound, having an agreed specification allows others to build tools around this specification. (i.e. auto-generation, integration). In theory, this makes development easier. OpenAPI achieved this and is now widely used in various tools including Amazon API Gateway.

The types of diagrams you listed above are great for describing software in useful ways, but none of them are rigid enough to spec out an async API.

I still need to review this spec to fully understand it, so I'm not promoting AsyncAPI. I like the motivation behind it.

edit: typo

I don't quite get it. Why can't I just enforce schema validation in my pub/sub handlers?

I see the YAML example completed here: https://www.asyncapi.com/docs/getting-started/servers/

    asyncapi: 2.0.0
    info:
      title: Hello world application
      version: '0.1.0'
    servers:
      production:
        url: broker.mycompany.com
        protocol: amqp
        description: This is "My Company" broker.
    channels:
      hello:
        publish:
          message:
            payload:
              type: string
              pattern: '^hello .+$'

This looks like a thin wrapper around sending a message to a message queue. What's the gain?

Where do you define what to do as a subscriber?

you have 2 operations in the spec, publish and subscribe.

above example already tells you what to do as a subscriber, as the document you shared describes an application that publishes a message

Yeah, a "Related Work" section would (potentially) be very reassuring.

What would be really cool is if this could serve as a front-end to e.g. SPIN model checker ( https://en.wikipedia.org/wiki/SPIN_model_checker https://en.wikipedia.org/wiki/Promela )

There appears to be far more details on the main website: https://www.asyncapi.com/ Not sure why the Github repo was submitted.

Websites can be embellished and misleading, also don't give a real sense of popularity and community support. I think a github repo is a thousand times better than a well "designed" landing page

I'd like to see an example on either landing point, both preferably.