curl --request PATCH \
  --url https://api.hubapi.com/crm-object-schemas/v3/schemas/{objectType} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "primaryDisplayProperty": "my_object_property",
  "requiredProperties": [
    "my_object_property"
  ],
  "searchableProperties": [
    "my_object_property"
  ]
}
'

{
  "createdAt": "2020-02-20T18:07:11.390Z",
  "id": "123456",
  "labels": {
    "plural": "My objects",
    "singular": "My object"
  },
  "metaType": "PORTAL_SPECIFIC",
  "name": "my_object",
  "portalId": 12345678,
  "primaryDisplayProperty": "my_object_property",
  "requiredProperties": [
    "my_object_property"
  ],
  "searchableProperties": [
    "my_object_property"
  ],
  "updatedAt": "2020-02-21T14:13:28.818002Z"
}