How to compose a schema from the success (right value) of an Either?

export const InitializeSchemasResult = S.Either({
    left: S.Union(SpannerError, ConfigStoreError,  ContainerCommunicationError),
    right: S.Struct({
        schemasInitialized: S.Number,
        totalSchemas: S.Number
    }),
});

    .addSuccess(InitializeSchemasResult.right)