Instead of ‘login’ and ‘password’ use your credentials from https://app.dataforseo.com/api-access

# Instead of 'login' and 'password' use your credentials from https://app.dataforseo.com/api-access \
login="login" 
password="password" 
cred="$(printf ${login}:${password} | base64)" 
curl --location --request GET "https://api.dataforseo.com/v3/appendix/errors" \
--header "Authorization: Basic ${cred}"  \
--header "Content-Type: application/json" \
--data-raw ''

<?php
// You can download this file from here https://api.dataforseo.com/v3/_examples/php/_php_RestClient.zip
require('RestClient.php');
$api_url = 'https://api.dataforseo.com/';
try {
	// Instead of 'login' and 'password' use your credentials from https://app.dataforseo.com/api-access
	$client = new RestClient($api_url, null, 'login', 'password');
} catch (RestClientException $e) {
	echo "\n";
	print "HTTP code: {$e->getHttpCode()}\n";
	print "Error code: {$e->getCode()}\n";
	print "Message: {$e->getMessage()}\n";
	print  $e->getTraceAsString();
	echo "\n";
	exit();
}
try {
	// using this method you can get a list of errors
	// GET /v3/appendix/errors
	$result = $client->get('/v3/appendix/errors');
	print_r($result);
	// do something with result
} catch (RestClientException $e) {
	echo "\n";
	print "HTTP code: {$e->getHttpCode()}\n";
	print "Error code: {$e->getCode()}\n";
	print "Message: {$e->getMessage()}\n";
	print  $e->getTraceAsString();
	echo "\n";
}
$client = null;
?>

from random import Random
from client import RestClient
# You can download this file from here https://api.dataforseo.com/v3/_examples/python/_python_Client.zip

client = RestClient("login", "password")
# using this method you can get a list of errors
# GET /v3/appendix/errors
response = client.get("/v3/appendix/errors")
# you can find the full list of the response codes here https://docs.dataforseo.com/v3/appendix/errors
if response["status_code"] == 20000:
    print(response)
    # do something with result
else:
    print("error. Code: %d Message: %s" % (response["status_code"], response["status_message"]))

const axios = require('axios');

axios({
    method: 'get',
    url: 'https://api.dataforseo.com/v3/appendix/errors',
    auth: {
        username: 'login',
        password: 'password'
    },
    headers: {
        'content-type': 'application/json'
    }
}).then(function (response) {
    var result = response['data']['tasks'][0]['result'];
    // Result data
    console.log(result);
}).catch(function (error) {
    console.log(error);
});

using Newtonsoft.Json;
using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;

namespace DataForSeoDemos
{
    public static partial class Demos
    {
        public static async Task appendix_errors()
        {
            var httpClient = new HttpClient
            {
                BaseAddress = new Uri("https://api.dataforseo.com/"),
                // Instead of 'login' and 'password' use your credentials from https://app.dataforseo.com/api-access                
                DefaultRequestHeaders = { Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(Encoding.ASCII.GetBytes("login:password"))) }
            };
            // using this method you can get a list of errors
            // GET /v3/appendix/errors
            var response = await httpClient.GetAsync("/v3/appendix/errors");
            var result = JsonConvert.DeserializeObject(await response.Content.ReadAsStringAsync());
            // you can find the full list of the response codes here https://docs.dataforseo.com/v3/appendix/errors
            if (result.status_code == 20000)
            {
                // do something with result
                Console.WriteLine(result);
            }
            else
                Console.WriteLine($"error. Code: {result.status_code} Message: {result.status_message}");
        }
    }
}

The above command returns JSON structured like this:

{
    "version": "0.1.20221214",
    "status_code": 20000,
    "status_message": "Ok.",
    "time": "0.0806 sec.",
    "cost": 0,
    "tasks_count": 1,
    "tasks_error": 0,
    "tasks": [
        {
            "id": "03302011-1535-0161-0000-99c1c52351b3",
            "status_code": 20000,
            "status_message": "Ok.",
            "time": "0.0000 sec.",
            "cost": 0,
            "result_count": 46,
            "path": [
                "v3",
                "appendix",
                "errors"
            ],
            "data": {
                "api": "appendix",
                "function": "errors"
            },
            "result": [
                {
                    "code": 20000,
                    "message": "Ok."
                },
                {
                    "code": 20100,
                    "message": "Task Created."
                },
                {
                    "code": 40000,
                    "message": "You can set only one task at a time."
                },
                {
                    "code": 40001,
                    "message": "This id is used by another client, check the id."
                },
                {
                    "code": 40002,
                    "message": "This id is used by another search engine, check the Path."
                },
                {
                    "code": 40003,
                    "message": "This id is used by another search type, check the Path."
                },
                {
                    "code": 40004,
                    "message": "This id is used by another function, check the id."
                },
                {
                    "code": 40006,
                    "message": "You can set no more than 100 tasks at a time."
                },
                {
                    "code": 40100,
                    "message": "You are not authorized to access this resource. See your login details here: https://app.dataforseo.com/api-access ."
                },
                {
                    "code": 40101,
                    "message": "Internal SE Server Error."
                },
                {
                    "code": 40102,
                    "message": "No Search Results."
                },
                {
                    "code": 40103,
                    "message": "Task execution failed, please try to resubmit the task."
                },
                {
                    "code": 40200,
                    "message": "Payment Required."
                },
                {
                    "code": 40201,
                    "message": "We noticed some unusual activity in your DataForSEO account, so we’ve temporarily paused access as a precaution. Please, reach out to our support team at support@dataforseo.com for more details, and we’ll work with you to resolve this quickly."
                },
                {
                    "code": 40202,
                    "message": "The rate-limit per minute has been exceeded."
                },
                {
                    "code": 40203,
                    "message": "The cost limit has been exceeded. You can modify your cost limit in the user panel https://app.dataforseo.com/api-settings ."
                },
                {
                    "code": 40204,
                    "message": "Access denied. Visit Plans and Subscriptions to activate your subscription and get access to this API: https://app.dataforseo.com/users/getrows ."
                },
                {
                    "code": 40205,
                    "message": "The duplicate task limit per hour has been exceeded. You can modify your limits in the user panel https://app.dataforseo.com/api-settings ."
                },
                {
                    "code": 40206,
                    "message": "The duplicate task limit per day has been exceeded. You can modify your limits in the user panel https://app.dataforseo.com/api-settings ."
                },
                {
                    "code": 40207,
                    "message": "Access denied. Your IP is not whitelisted. You can modify your IP whitelist in the user panel https://app.dataforseo.com/api-access ."
                },
                {
                    "code": 40209,
                    "message": "Too many simultaneous queries."
                },
                {
                    "code": 40210,
                    "message": "Insufficient Funds. Your account's balance is too low to complete this request."
                },
                {
                    "code": 40400,
                    "message": "Not Found."
                },
                {
                    "code": 40401,
                    "message": "Task Not Found."
                },
                {
                    "code": 40402,
                    "message": "Invalid Path."
                },
                {
                    "code": 40403,
                    "message": "Results Expired."
                },
                {
                    "code": 40404,
                    "message": "No Prepared Data Found. Please Contact Our Support Team."
                },
                {
                    "code": 40405,
                    "message": "Textual content on the target page is insufficient."
                },
                {
                    "code": 40406,
                    "message": "Requested page was not submitted for crawling."
                },
                {
                    "code": 40501,
                    "message": "Invalid Field."
                },
                {
                    "code": 40502,
                    "message": "POST Data Is Empty."
                },
                {
                    "code": 40503,
                    "message": "POST Data Is Invalid."
                },
                {
                    "code": 40504,
                    "message": "The number of intersecting keywords for the specified domains exceeds 10 million. Try specifying different domains."
                },
                {
                    "code": 40505,
                    "message": "You are using old data."
                },
                {
                    "code": 40506,
                    "message": "Unknown Fields in POST Data."
                },
                {
                    "code": 40601,
                    "message": "Task Handed."
                },
                {
                    "code": 40602,
                    "message": "Task In Queue."
                },
                {
                    "code": 50000,
                    "message": "Internal Error."
                },
                {
                    "code": 50001,
                    "message": "Error While Checking the Balance."
                },
                {
                    "code": 50100,
                    "message": "Not Implemented."
                },
                {
                    "code": 50301,
                    "message": "3rd Party API Service Unavailable."
                },
                {
                    "code": 50303,
                    "message": "Update in progress. Please try after a few minutes."
                },
                {
                    "code": 50304,
                    "message": "This function temporarily unavailable. Please contact support for more information."
                },
                {
                    "code": 50401,
                    "message": "Internal Error - Timeout."
                },
                {
                    "code": 50402,
                    "message": "Target page took too long to respond."
                }
            ]
        }
    ]
}