How can I replace the generated OpenAPI spec in Swagger (JAX-RS + OpenApiResource) with a custom OpenAPI object?

I'm using Swagger with Jersey (JAX-RS) to serve API documentation. I configure Swagger like this:

ResourceConfig swaggerResourceConfig = new ResourceConfig()
    .packages("io.swagger.v3.jaxrs2.integration.resources")
    .register(OpenApiResource.class)
    .register(SwaggerSerializers.class)
    .register(AcceptHeaderOpenApiResource.class)
    .property("jersey.config.server.wadl.disableWadl", true);

SwaggerConfiguration oasConfig = new SwaggerConfiguration()
    .openApi(baseModel) // <-- I would want to serve the modified object, but can't at this point
    .prettyPrint(true)
    .resourcePackages(Set.of("my.api.package"));

OpenApiContext openApiCtx = new JaxrsOpenApiContextBuilder()
    .openApiConfiguration(oasConfig)
    .buildContext(true);

I have many endpoints where the ApiResponse.description is never set, so Swagger-UI shows errors: Structural error at {PATH} should have required property 'description' missingProperty: description. I wrote a helper function that traverses the generated OpenAPI model and fills in empty descriptions, which I tested out and it works:

public OpenAPI patchMissingDescriptions(OpenAPI openAPI) {
    if (openAPI.getPaths() != null) {
        for (Entry<String, PathItem> entry : openAPI.getPaths().entrySet()) {
            for (Operation operation : entry.getValue().readOperations()) {
                if (operation.getResponses() != null) {
                    for (Entry<String, ApiResponse> respEntry : operation.getResponses().entrySet()) {
                        ApiResponse response = respEntry.getValue();
                        if (response.getDescription() == null) {
                            response.setDescription("some description");
                        }
                    }
                }
            }
        }
    }
    return openAPI;
}

Problem:

I need to invoke patchMissingDescriptions() after the OpenAPI model is built but before Jersey serves the JSON/YAML docs.
Calling read() on the OpenApiContext to obtain the OpenAPI is prohibitively slow due to deep reflection so I can't use this.

What I'm looking for

An extension point in Swagger-Core or JAX-RS integration that lets me mutate the in-memory OpenAPI object exactly once, after it’s built but before it’s cached/serialized.
Or a recommended best practice / pattern for filling in default values, especially response descriptions without duplicating the scanning logic.

what I've tried:

Manually calling ctx.read() each time but my app just freezes due to reflection
ContainerResponseFilter on /openapi.json (runs after serialization).

Solution

What I needed to do was:

add a custom Reader class to my SwaggerConfiguration:

SwaggerConfiguration oasConfig = new SwaggerConfiguration()
    .openApi(baseModel)
    .readerClass(MyCustomReader.class.getName()) // <- HERE
    .prettyPrint(true)
    .resourcePackages(Set.of("my.api.package"));

implement the Reader class extending io.swagger.v3.jaxrs2.Reader; and overriding the read method

public class MyCustomReader extends Reader {

  @Override
  public OpenAPI read(Class<?> cls,
                      String parentPath, 
                      String parentMethod, 
                      boolean isSubresource,
                      RequestBody parentRequestBody, 
                      ApiResponses apiResponses,
                      Set<String> parentTags,
                      List<Parameter> parentParameters,
                      Set<Class<?>> scannedResources)
 {
    OpenAPI openAPI = super.read(cls, parentPath, parentMethod, isSubresource,                parentRequestBody, apiResponses,
      parentTags, parentParameters, scannedResources);
    return populateMissingDescriptions(openAPI);
  }

  public static OpenAPI populateMissingDescriptions(OpenAPI openAPI) {
    if (openAPI.getPaths() != null) {
      for (Entry<String, PathItem> entry : openAPI.getPaths().entrySet()) {
        String path = entry.getKey();
        PathItem pathItem = entry.getValue();
        for (Operation operation : pathItem.readOperations()) {
          if (operation.getResponses() != null) {
            for (Entry<String, ApiResponse> e : operation.getResponses().entrySet()) {
              String status = e.getKey();
              ApiResponse response = e.getValue();
              if (response.getDescription() == null) {
                response.setDescription("");
              }
            }
          }
        }
      }
    }
    return openAPI;
  }
}