curl --request POST \
  --url https://api.hubapi.com/crm/v3/extensions/cards-dev/{appId} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "actions": {
    "baseUrls": [
      "https://www.example.com/hubspot"
    ]
  },
  "display": {
    "properties": [
      {
        "dataType": "STRING",
        "label": "Pets Name",
        "name": "pet_name"
      }
    ]
  },
  "fetch": {
    "objectTypes": [
      {
        "name": "contacts",
        "propertiesToSend": [
          "email",
          "firstname"
        ]
      }
    ],
    "targetUrl": "https://www.example.com/hubspot/target"
  },
  "title": "PetSpot"
}
'

import requests

url = "https://api.hubapi.com/crm/v3/extensions/cards-dev/{appId}"

payload = {
    "actions": { "baseUrls": ["https://www.example.com/hubspot"] },
    "display": { "properties": [
            {
                "dataType": "STRING",
                "label": "Pets Name",
                "name": "pet_name"
            }
        ] },
    "fetch": {
        "objectTypes": [
            {
                "name": "contacts",
                "propertiesToSend": ["email", "firstname"]
            }
        ],
        "targetUrl": "https://www.example.com/hubspot/target"
    },
    "title": "PetSpot"
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    actions: {baseUrls: ['https://www.example.com/hubspot']},
    display: {properties: [{dataType: 'STRING', label: 'Pets Name', name: 'pet_name'}]},
    fetch: {
      objectTypes: [{name: 'contacts', propertiesToSend: ['email', 'firstname']}],
      targetUrl: 'https://www.example.com/hubspot/target'
    },
    title: 'PetSpot'
  })
};

fetch('https://api.hubapi.com/crm/v3/extensions/cards-dev/{appId}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.hubapi.com/crm/v3/extensions/cards-dev/{appId}",
  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([
    'actions' => [
        'baseUrls' => [
                'https://www.example.com/hubspot'
        ]
    ],
    'display' => [
        'properties' => [
                [
                                'dataType' => 'STRING',
                                'label' => 'Pets Name',
                                'name' => 'pet_name'
                ]
        ]
    ],
    'fetch' => [
        'objectTypes' => [
                [
                                'name' => 'contacts',
                                'propertiesToSend' => [
                                                                'email',
                                                                'firstname'
                                ]
                ]
        ],
        'targetUrl' => 'https://www.example.com/hubspot/target'
    ],
    'title' => 'PetSpot'
  ]),
  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;
}

package main

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

func main() {

	url := "https://api.hubapi.com/crm/v3/extensions/cards-dev/{appId}"

	payload := strings.NewReader("{\n  \"actions\": {\n    \"baseUrls\": [\n      \"https://www.example.com/hubspot\"\n    ]\n  },\n  \"display\": {\n    \"properties\": [\n      {\n        \"dataType\": \"STRING\",\n        \"label\": \"Pets Name\",\n        \"name\": \"pet_name\"\n      }\n    ]\n  },\n  \"fetch\": {\n    \"objectTypes\": [\n      {\n        \"name\": \"contacts\",\n        \"propertiesToSend\": [\n          \"email\",\n          \"firstname\"\n        ]\n      }\n    ],\n    \"targetUrl\": \"https://www.example.com/hubspot/target\"\n  },\n  \"title\": \"PetSpot\"\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))

}

HttpResponse<String> response = Unirest.post("https://api.hubapi.com/crm/v3/extensions/cards-dev/{appId}")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"actions\": {\n    \"baseUrls\": [\n      \"https://www.example.com/hubspot\"\n    ]\n  },\n  \"display\": {\n    \"properties\": [\n      {\n        \"dataType\": \"STRING\",\n        \"label\": \"Pets Name\",\n        \"name\": \"pet_name\"\n      }\n    ]\n  },\n  \"fetch\": {\n    \"objectTypes\": [\n      {\n        \"name\": \"contacts\",\n        \"propertiesToSend\": [\n          \"email\",\n          \"firstname\"\n        ]\n      }\n    ],\n    \"targetUrl\": \"https://www.example.com/hubspot/target\"\n  },\n  \"title\": \"PetSpot\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.hubapi.com/crm/v3/extensions/cards-dev/{appId}")

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  \"actions\": {\n    \"baseUrls\": [\n      \"https://www.example.com/hubspot\"\n    ]\n  },\n  \"display\": {\n    \"properties\": [\n      {\n        \"dataType\": \"STRING\",\n        \"label\": \"Pets Name\",\n        \"name\": \"pet_name\"\n      }\n    ]\n  },\n  \"fetch\": {\n    \"objectTypes\": [\n      {\n        \"name\": \"contacts\",\n        \"propertiesToSend\": [\n          \"email\",\n          \"firstname\"\n        ]\n      }\n    ],\n    \"targetUrl\": \"https://www.example.com/hubspot/target\"\n  },\n  \"title\": \"PetSpot\"\n}"

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

{
  "actions": {
    "baseUrls": [
      "https://www.example.com/hubspot"
    ]
  },
  "auditHistory": [
    {
      "applicationId": 123,
      "changedAt": 123,
      "initiatingUserId": 123,
      "objectTypeId": 123
    }
  ],
  "display": {
    "properties": [
      {
        "label": "<string>",
        "name": "<string>",
        "options": [
          {
            "label": "<string>",
            "name": "<string>"
          }
        ]
      }
    ]
  },
  "fetch": {
    "objectTypes": [
      {
        "propertiesToSend": [
          "<string>"
        ]
      }
    ],
    "targetUrl": "<string>"
  },
  "id": "<string>",
  "title": "<string>",
  "createdAt": "2023-11-07T05:31:56Z",
  "updatedAt": "2023-11-07T05:31:56Z"
}

{
  "message": "Invalid input (details will vary based on the error)",
  "correlationId": "aeb5f871-7f07-4993-9211-075dc63e7cbf",
  "category": "VALIDATION_ERROR",
  "links": {
    "knowledge-base": "https://www.hubspot.com/products/service/knowledge-base"
  }
}