diff --git a/staging/src/k8s.io/sample-controller/README.md b/staging/src/k8s.io/sample-controller/README.md
index cbd55a51a7c..3b73b33a8b3 100644
--- a/staging/src/k8s.io/sample-controller/README.md
+++ b/staging/src/k8s.io/sample-controller/README.md
@@ -126,6 +126,8 @@ type User struct {
 }
 ```
 
+Note, the JSON tag `json:` is required on all user facing fields within your type. Typically API types contain only user facing fields. When the JSON tag is omitted from the field, Kubernetes generators consider the field to be internal and will not expose the field in their generated external output. For example, this means that the field would not be included in a generated CRD schema.
+
 ## Validation
 
 To validate custom resources, use the [`CustomResourceValidation`](https://kubernetes.io/docs/tasks/access-kubernetes-api/extend-api-custom-resource-definitions/#validation) feature. Validation in the form of a [structured schema](https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/#specifying-a-structural-schema) is mandatory to be provided for `apiextensions.k8s.io/v1`.