How to describe a tuple in AsyncAPI?

[RobinTail]

Hello community,

I'd like to describe a service running over Socket.IO protocol (uses Websocket for transport) using AsyncAPI v3.0.0.

The payloads of the Socket.IO messages are tuples — arrays having fixed length and the elements of different types.

JSON Schema Draft 2020 offers the prefixItems property in the Schema Object for that purpose, but the Schema Object of AsyncAPI does not support it, and as per my understanding, is not going to in the nearest future. Moreover, even the schemaFormat property does not allow me to set the format to a Draft higher than 07 or the format of OpenAPI 3.1 which supports prefixItems.

What would be your advice on describing a payload like this?:

type ChatMessage = [ string, { from: string } ]

So far I invented a hacky approach of describing those tuples as objects having numeric props, because arrays are objects in JavaScript.

        payload:
          type: object
          format: tuple
          properties:
            "0":
              type: string
              description: message
              examples:
                - Hello there!
            "1":
              type: object
              properties:
                from:
                  type: string
                  description: the ID of author
              required:
                - from
              description: extra info
              examples:
                - from: 123abc
          required:
            - "0"
            - "1"
          additionalProperties: false

What would be a community advice on that topic? Is there a better way?

[RobinTail]

The JSON Schema Draft-07, which is per my understanding Async API is based on, also say that items can be array of Schemas, so that tuples could be described, but AsyncAPI 3.0.0 does not support it as well — I tried it and it does not pass the validation.

[RobinTail]

I figured out what was the issue with items approach — it does work, but for non-empty tuples only.
If items is an empty array, validator of Studio shows a huge pile of errors pointing to wrong lines.
But once I restricted items to describe only non-empty tuples, it began working as expected:

Here is my implementation for those might having similar issue:

        payload:
          type: array
          items:
            - type: string
              description: message
            - type: object
              properties:
                from:
                  type: string
                  description: the ID of author
              required:
                - from
              description: extra info
          additionalItems: false