Metrics and alerts configuration in open search

Question

I am using plugins to export data from opentelementry to open search.

I am using below configurations

   metrics-pipeline:
     source:
        otel_metrics_source:
          ssl: false
     processor:
        - otel_metrics_raw_processor:
     sink:
        - opensearch:
             hosts: ["https://<domain-name>:443"]
             insecure: true
             username: "username"
             password: "password
             index: metrics-otel-v1-%{yyyy.MM.dd}

With the above configuration I am able to see all the traces along with trace error rate and traces over time details but

As per the documentation, metrics feature is included recently so I am not able to find proper documentation.

I am trying to configure metrics in open search, I can see only some options under visualization like sum, count etc so please provide any inputs on how to configure proper metrics in opensearch

Also Data prepper has created an index "otel-v1-apm-span" by default without any time field so when I am trying to configure alerts or detectors, it is asking for time field in the index.

Please let me know if I am missing anything.

Any inputs will be appreciated.