curl --request PUT \
  --url https://int-api.mx.com/users/{user_guid}/transaction_rules/{transaction_rule_guid} \
  --header 'Authorization: Basic <encoded-value>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "transaction_rule": {
    "category_guid": "CAT-b1de2a04-db08-b6ed-f6fe-ca2f5b11c2d0",
    "description": "Wal-mart food storage",
    "match_description": "Wal-mart"
  }
}
'

import requests

url = "https://int-api.mx.com/users/{user_guid}/transaction_rules/{transaction_rule_guid}"

payload = { "transaction_rule": {
        "category_guid": "CAT-b1de2a04-db08-b6ed-f6fe-ca2f5b11c2d0",
        "description": "Wal-mart food storage",
        "match_description": "Wal-mart"
    } }
headers = {
    "Authorization": "Basic <encoded-value>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'PUT',
  headers: {Authorization: 'Basic <encoded-value>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    transaction_rule: {
      category_guid: 'CAT-b1de2a04-db08-b6ed-f6fe-ca2f5b11c2d0',
      description: 'Wal-mart food storage',
      match_description: 'Wal-mart'
    }
  })
};

fetch('https://int-api.mx.com/users/{user_guid}/transaction_rules/{transaction_rule_guid}', 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://int-api.mx.com/users/{user_guid}/transaction_rules/{transaction_rule_guid}",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "PUT",
  CURLOPT_POSTFIELDS => json_encode([
    'transaction_rule' => [
        'category_guid' => 'CAT-b1de2a04-db08-b6ed-f6fe-ca2f5b11c2d0',
        'description' => 'Wal-mart food storage',
        'match_description' => 'Wal-mart'
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Basic <encoded-value>",
    "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://int-api.mx.com/users/{user_guid}/transaction_rules/{transaction_rule_guid}"

	payload := strings.NewReader("{\n  \"transaction_rule\": {\n    \"category_guid\": \"CAT-b1de2a04-db08-b6ed-f6fe-ca2f5b11c2d0\",\n    \"description\": \"Wal-mart food storage\",\n    \"match_description\": \"Wal-mart\"\n  }\n}")

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

	req.Header.Add("Authorization", "Basic <encoded-value>")
	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.put("https://int-api.mx.com/users/{user_guid}/transaction_rules/{transaction_rule_guid}")
  .header("Authorization", "Basic <encoded-value>")
  .header("Content-Type", "application/json")
  .body("{\n  \"transaction_rule\": {\n    \"category_guid\": \"CAT-b1de2a04-db08-b6ed-f6fe-ca2f5b11c2d0\",\n    \"description\": \"Wal-mart food storage\",\n    \"match_description\": \"Wal-mart\"\n  }\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://int-api.mx.com/users/{user_guid}/transaction_rules/{transaction_rule_guid}")

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

request = Net::HTTP::Put.new(url)
request["Authorization"] = 'Basic <encoded-value>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"transaction_rule\": {\n    \"category_guid\": \"CAT-b1de2a04-db08-b6ed-f6fe-ca2f5b11c2d0\",\n    \"description\": \"Wal-mart food storage\",\n    \"match_description\": \"Wal-mart\"\n  }\n}"

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

{
  "transaction_rule": {
    "category_guid": "CAT-b1de2a04-db08-b6ed-f6fe-ca2f5b11c2d0",
    "created_at": "2018-10-02T22:00:50+00:00",
    "description": "Wal-mart food storage",
    "guid": "TXR-a080e0f9-a2d4-4d6f-9e03-672cc357a4d3",
    "match_description": "Wal-mart",
    "updated_at": "2018-10-02T23:54:40+00:00",
    "user_guid": "USR-22fc3203-b3e6-8340-43db-8e50b2f56995"
  }
}