curl --request GET \
  --url https://drb.coinbase.com/api/v2/private/get_max_order_size \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "private/get_max_order_size",
  "params": {
    "instrument_name": "BTC-PERPETUAL",
    "price": 65000
  }
}
'

import requests

url = "https://drb.coinbase.com/api/v2/private/get_max_order_size"

payload = {
    "id": 1,
    "jsonrpc": "2.0",
    "method": "private/get_max_order_size",
    "params": {
        "instrument_name": "BTC-PERPETUAL",
        "price": 65000
    }
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'GET',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    id: 1,
    jsonrpc: '2.0',
    method: 'private/get_max_order_size',
    params: {instrument_name: 'BTC-PERPETUAL', price: 65000}
  })
};

fetch('https://drb.coinbase.com/api/v2/private/get_max_order_size', 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://drb.coinbase.com/api/v2/private/get_max_order_size",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "GET",
  CURLOPT_POSTFIELDS => json_encode([
    'id' => 1,
    'jsonrpc' => '2.0',
    'method' => 'private/get_max_order_size',
    'params' => [
        'instrument_name' => 'BTC-PERPETUAL',
        'price' => 65000
    ]
  ]),
  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://drb.coinbase.com/api/v2/private/get_max_order_size"

	payload := strings.NewReader("{\n  \"id\": 1,\n  \"jsonrpc\": \"2.0\",\n  \"method\": \"private/get_max_order_size\",\n  \"params\": {\n    \"instrument_name\": \"BTC-PERPETUAL\",\n    \"price\": 65000\n  }\n}")

	req, _ := http.NewRequest("GET", 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.get("https://drb.coinbase.com/api/v2/private/get_max_order_size")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"id\": 1,\n  \"jsonrpc\": \"2.0\",\n  \"method\": \"private/get_max_order_size\",\n  \"params\": {\n    \"instrument_name\": \"BTC-PERPETUAL\",\n    \"price\": 65000\n  }\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://drb.coinbase.com/api/v2/private/get_max_order_size")

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

request = Net::HTTP::Get.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"id\": 1,\n  \"jsonrpc\": \"2.0\",\n  \"method\": \"private/get_max_order_size\",\n  \"params\": {\n    \"instrument_name\": \"BTC-PERPETUAL\",\n    \"price\": 65000\n  }\n}"

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

{
  "id": 1,
  "jsonrpc": "2.0",
  "result": {
    "buy_price": 65000,
    "max_tradable_amount": {
      "buy_notional": 125000,
      "sell_notional": 150000
    },
    "max_tradable_amount_reduce_only": {
      "buy_notional": 50000,
      "sell_notional": 0
    },
    "sell_price": 65000
  }
}