POST
    /custom_fields
  
  curl \
 --request POST 'https://stg.getfoundation.com/api/external/v1/custom_fields' \
 --header "X-API-Key: $API_KEY" \
 --header "Content-Type: application/json" \
 --data '{"custom_field":{"key":"country_of_origin","label":"Country Of Origin","entity_type":"item","value_type":"string","options":["USA","China","India"]}}'
    
        Request examples
  
  {
  "custom_field": {
    "key": "country_of_origin",
    "label": "Country Of Origin",
    "entity_type": "item",
    "value_type": "string",
    "options": [
      "USA",
      "China",
      "India"
    ]
  }
}
        Response examples (201)
  
  {
  "id": "9aa62446-c3b0-42f5-8027-3648daed9d73",
  "key": "country_of_origin",
  "label": "Country Of Origin",
  "entity_type": "item",
  "value_type": "string",
  "options": [
    "USA",
    "China",
    "India"
  ],
  "created_at": "2025-05-04T09:42:00Z",
  "updated_at": "2025-05-04T09:42:00Z"
}