curl --request POST \
  --url https://{organization}.rescueconsole.com/api/shifts/custom-fields \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "entity_type": "volunteer_event",
  "field_key": "venue_contact",
  "field_label": "Venue contact",
  "field_type": "text"
}
'

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    entity_type: 'volunteer_event',
    field_key: 'venue_contact',
    field_label: 'Venue contact',
    field_type: 'text'
  })
};

fetch('https://{organization}.rescueconsole.com/api/shifts/custom-fields', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://{organization}.rescueconsole.com/api/shifts/custom-fields"

payload = {
    "entity_type": "volunteer_event",
    "field_key": "venue_contact",
    "field_label": "Venue contact",
    "field_type": "text"
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

{
  "id": "<string>",
  "entity_type": "volunteer_event",
  "field_key": "<string>",
  "field_label": "<string>",
  "field_type": "text",
  "options": [
    "<string>"
  ],
  "required": true,
  "sort_order": 123
}

{
  "error": "house_trained must be 1, 0 or null (not assessed)"
}

{
  "error": "house_trained must be 1, 0 or null (not assessed)"
}

{
  "error": "house_trained must be 1, 0 or null (not assessed)"
}

{
  "error": "house_trained must be 1, 0 or null (not assessed)"
}