curl --request POST \
  --url https://api.folk.app/v1/groups/{groupId}/custom-fields/{entityType} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "type": "textField",
  "name": "<string>"
}
'

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({type: 'textField', name: '<string>'})
};

fetch('https://api.folk.app/v1/groups/{groupId}/custom-fields/{entityType}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://api.folk.app/v1/groups/{groupId}/custom-fields/{entityType}"

payload = {
    "type": "textField",
    "name": "<string>"
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.text)

require 'uri'
require 'net/http'

url = URI("https://api.folk.app/v1/groups/{groupId}/custom-fields/{entityType}")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"type\": \"textField\",\n  \"name\": \"<string>\"\n}"

response = http.request(request)
puts response.read_body

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.folk.app/v1/groups/{groupId}/custom-fields/{entityType}"

	payload := strings.NewReader("{\n  \"type\": \"textField\",\n  \"name\": \"<string>\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.folk.app/v1/groups/{groupId}/custom-fields/{entityType}",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'type' => 'textField',
    'name' => '<string>'
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

{
  "data": {
    "name": "Status",
    "type": "singleSelect",
    "options": [
      {
        "id": "gcfo_bc984b3f-0386-434d-82d7-a91eb6badd71",
        "label": "Active",
        "color": "#ffffff"
      },
      {
        "id": "gcfo_28cf7f0a-fb0a-4b6b-9d47-3f5f2e3f1a3f",
        "label": "Inactive",
        "color": "#000000"
      }
    ]
  }
}

{
  "error": {
    "code": "INVALID_REQUEST",
    "message": "The request was invalid.",
    "documentationUrl": "https://developer.folk.app/api-reference/errors#bad-request",
    "requestId": "123e4567-e89b-12d3-a456-426614174000",
    "timestamp": "2025-10-01T12:00:00Z"
  }
}

{
  "error": {
    "code": "UNAUTHORIZED",
    "message": "No valid API key provided.",
    "documentationUrl": "https://developer.folk.app/api-reference/errors#unauthorized",
    "requestId": "123e4567-e89b-12d3-a456-426614174000",
    "timestamp": "2025-10-01T12:00:00Z"
  }
}

{
  "error": {
    "code": "FORBIDDEN",
    "message": "The API key doesn’t have permissions to perform the request.",
    "documentationUrl": "https://developer.folk.app/api-reference/errors#forbidden",
    "requestId": "123e4567-e89b-12d3-a456-426614174000",
    "timestamp": "2025-10-01T12:00:00Z"
  }
}

{
  "error": {
    "code": "RESOURCE_NOT_FOUND",
    "message": "The requested resource was not found.",
    "documentationUrl": "https://developer.folk.app/api-reference/errors#not-found",
    "requestId": "123e4567-e89b-12d3-a456-426614174000",
    "timestamp": "2025-10-01T12:00:00Z"
  }
}

{
  "error": {
    "code": "UNPROCESSABLE_ENTITY",
    "message": "Invalid query parameters",
    "documentationUrl": "https://developer.folk.app/api-reference/errors#unprocessable-entity",
    "details": {
      "issues": [
        {
          "code": "too_small",
          "minimum": 1,
          "type": "number",
          "inclusive": true,
          "exact": false,
          "message": "Number must be greater than or equal to 1",
          "path": [
            "limit"
          ]
        }
      ]
    },
    "requestId": "123e4567-e89b-12d3-a456-426614174000",
    "timestamp": "2025-10-01T12:00:00Z"
  }
}

{
  "error": {
    "code": "RATE_LIMIT_EXCEEDED",
    "message": "The rate limit has been exceeded.",
    "documentationUrl": "https://developer.folk.app/api-reference/errors#rate-limiting",
    "requestId": "123e4567-e89b-12d3-a456-426614174000",
    "timestamp": "2025-10-01T12:00:00Z",
    "details": {
      "limit": 1000,
      "remaining": 0,
      "retryAfter": "2025-10-01T12:00:00Z"
    }
  }
}

{
  "error": {
    "code": "INTERNAL_SERVER_ERROR",
    "message": "An internal server error occurred.",
    "documentationUrl": "https://developer.folk.app/api-reference/errors#internal-server-error",
    "requestId": "123e4567-e89b-12d3-a456-426614174000",
    "timestamp": "2025-10-01T12:00:00Z"
  }
}

{
  "error": {
    "code": "SERVICE_UNAVAILABLE",
    "message": "The service is currently unavailable.",
    "documentationUrl": "https://developer.folk.app/api-reference/errors#service-unavailable",
    "requestId": "123e4567-e89b-12d3-a456-426614174000",
    "timestamp": "2025-10-01T12:00:00Z"
  }
}