crd-crontab.yaml

apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  name: crontabs.stable.example.com
spec:
  group: stable.example.com
  versions:
    - name: v1
      served: true
      storage: true
      schema:
        openAPIV3Schema:
          type: object
          properties:
            spec:
              type: object
              properties:
                cronSpec:
                  type: string
                image:
                  type: string
                replicas:
                  type: integer
  scope: Namespaced
  names:
    plural: crontabs
    singular: crontab
    kind: CronTab
    shortNames:
    - ct

swagger.json

    "com.example.stable.v1.CronTab": {
      "type": "object",
      "properties": {
        "apiVersion": {
          "description": "APIVersion defines the versioned schema of this representation of an object. Servers should convert recognized schemas to the latest internal value, and may reject unrecognized values. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources",
          "type": "string"
        },
        "kind": {
          "description": "Kind is a string value representing the REST resource this object represents. Servers may infer this from the endpoint the client submits requests to. Cannot be updated. In CamelCase. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds",
          "type": "string"
        },
        "metadata": {
          "description": "Standard object's metadata. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata",
          "$ref": "#/definitions/io.k8s.apimachinery.pkg.apis.meta.v1.ObjectMeta_v2"
        },
        "spec": {
          "type": "object",
          "properties": {
            "cronSpec": {
              "type": "string"
            },
            "image": {
              "type": "string"
            },
            "replicas": {
              "type": "integer"
            }
          }
        }
      },
      "x-kubernetes-group-version-kind": [
        {
          "group": "stable.example.com",
          "kind": "CronTab",
          "version": "v1"
        }
      ]
    }

using swagger.json:

• name should be deducible via <kind>.<group>
• group, kind & version can be taken from "x-kubernetes-group-version-kind"
• scope is missing