OpenAPI specification support in IS right now is limited to importing an OpenAPI document to generate the provider or consumer.
Generating OpenAPI document from a resource is in the pipeline for future releases. But still, we haven’t considered using third party resources like SOQL resources. But this can be good addition for that feature. We’ll definitely consider this.
Just an update, I manually created an openAPI specs for query resource and successfully imported in IS. I was able to retrieve records from Salesforce using my query but I still have issues on the response. It appears content of the response are not being encoded properly even adding conent-type or encoding properties in the openAPI specification.