diff --git a/composer.json b/composer.json
index 302b9ca..16f54b1 100644
--- a/composer.json
+++ b/composer.json
@@ -6,7 +6,8 @@
   "require": {
     "php": ">= 7.4",
     "ext-dom": "*",
-    "ext-soap": "*"
+    "ext-soap": "*",
+    "justinrainbow/json-schema": "5.2.12"
   },
   "require-dev": {
     "squizlabs/php_codesniffer": "^3.6.0"
diff --git a/composer.lock b/composer.lock
index 83cc9f6..fc09151 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,21 +4,92 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "b074362b32310c1261001900cd7dc81c",
-    "packages": [],
+    "content-hash": "a0a67ee09c999329c4395b2e94bc0d65",
+    "packages": [
+        {
+            "name": "justinrainbow/json-schema",
+            "version": "5.2.12",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/justinrainbow/json-schema.git",
+                "reference": "ad87d5a5ca981228e0e205c2bc7dfb8e24559b60"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/justinrainbow/json-schema/zipball/ad87d5a5ca981228e0e205c2bc7dfb8e24559b60",
+                "reference": "ad87d5a5ca981228e0e205c2bc7dfb8e24559b60",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.3.3"
+            },
+            "require-dev": {
+                "friendsofphp/php-cs-fixer": "~2.2.20||~2.15.1",
+                "json-schema/json-schema-test-suite": "1.2.0",
+                "phpunit/phpunit": "^4.8.35"
+            },
+            "bin": [
+                "bin/validate-json"
+            ],
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "5.0.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "JsonSchema\\": "src/JsonSchema/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Bruno Prieto Reis",
+                    "email": "bruno.p.reis@gmail.com"
+                },
+                {
+                    "name": "Justin Rainbow",
+                    "email": "justin.rainbow@gmail.com"
+                },
+                {
+                    "name": "Igor Wiedler",
+                    "email": "igor@wiedler.ch"
+                },
+                {
+                    "name": "Robert Schönthal",
+                    "email": "seroscho@googlemail.com"
+                }
+            ],
+            "description": "A library to validate a json schema.",
+            "homepage": "https://github.com/justinrainbow/json-schema",
+            "keywords": [
+                "json",
+                "schema"
+            ],
+            "support": {
+                "issues": "https://github.com/justinrainbow/json-schema/issues",
+                "source": "https://github.com/justinrainbow/json-schema/tree/5.2.12"
+            },
+            "time": "2022-04-13T08:02:27+00:00"
+        }
+    ],
     "packages-dev": [
         {
             "name": "squizlabs/php_codesniffer",
-            "version": "3.6.2",
+            "version": "3.7.2",
             "source": {
                 "type": "git",
                 "url": "https://github.com/squizlabs/PHP_CodeSniffer.git",
-                "reference": "5e4e71592f69da17871dba6e80dd51bce74a351a"
+                "reference": "ed8e00df0a83aa96acf703f8c2979ff33341f879"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/squizlabs/PHP_CodeSniffer/zipball/5e4e71592f69da17871dba6e80dd51bce74a351a",
-                "reference": "5e4e71592f69da17871dba6e80dd51bce74a351a",
+                "url": "https://api.github.com/repos/squizlabs/PHP_CodeSniffer/zipball/ed8e00df0a83aa96acf703f8c2979ff33341f879",
+                "reference": "ed8e00df0a83aa96acf703f8c2979ff33341f879",
                 "shasum": ""
             },
             "require": {
@@ -54,14 +125,15 @@
             "homepage": "https://github.com/squizlabs/PHP_CodeSniffer",
             "keywords": [
                 "phpcs",
-                "standards"
+                "standards",
+                "static analysis"
             ],
             "support": {
                 "issues": "https://github.com/squizlabs/PHP_CodeSniffer/issues",
                 "source": "https://github.com/squizlabs/PHP_CodeSniffer",
                 "wiki": "https://github.com/squizlabs/PHP_CodeSniffer/wiki"
             },
-            "time": "2021-12-12T21:44:58+00:00"
+            "time": "2023-02-22T23:07:41+00:00"
         }
     ],
     "aliases": [],
diff --git a/src/Downloader.php b/src/Downloader.php
new file mode 100644
index 0000000..c9e1e8d
--- /dev/null
+++ b/src/Downloader.php
@@ -0,0 +1,99 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Fykosak\FKSDBDownloaderCore;
+
+use JsonSchema\Constraints\Constraint;
+use JsonSchema\Validator;
+
+require __DIR__ . '/../vendor/autoload.php';
+
+class Downloader
+{
+    private array $config;
+
+    public function __construct(array $config)
+    {
+        $this->config = $config;
+    }
+
+    /**
+     * @return mixed
+     * @throws DownloaderException
+     */
+    public function download(string $app, string $source, array $arguments)
+    {
+        $config = $this->config[$app];
+        $this->validateRequest($arguments, $app, $source);
+
+        $options = [
+            'http' => [
+                'header' => "Content-type: application/x-www-form-urlencoded\r\n" .
+                    "Authorization: Basic " . base64_encode($config['username'] . ':' . $config['password']),
+                'method' => 'GET',
+                'content' => http_build_query($arguments),
+            ],
+        ];
+        $context = stream_context_create($options);
+
+        $result = file_get_contents(
+            $this->config[$app]['url'] . $source
+            . '?' . http_build_query($arguments),
+            false,
+            $context
+        );
+        if ($result === false) {
+            restore_error_handler();
+            throw new DownloaderException(error_get_last()['message']);
+        }
+        $this->validateResponse(json_decode($result), $app, $source);
+        return $result;
+    }
+
+    /**
+     * @throws DownloaderException
+     */
+    private function validateRequest(array $arguments, string $app, string $source): void
+    {
+        $this->validate(__DIR__ . DIRECTORY_SEPARATOR .
+            $app . DIRECTORY_SEPARATOR .
+            $source . DIRECTORY_SEPARATOR . 'request.json', $arguments);
+    }
+
+    /**
+     * @throws DownloaderException
+     */
+    private function validate(string $schemaFile, array $arguments): void
+    {
+        try {
+            $validator = new Validator();
+            $validator->validate($arguments, (object)[
+                '$ref' => 'file://' . $schemaFile,
+            ], Constraint::CHECK_MODE_TYPE_CAST);
+
+            if ($validator->isValid()) {
+                return;
+            } else {
+                $errors = '';
+                foreach ($validator->getErrors() as $error) {
+                    var_dump($error);
+                    $errors .= join(', ', $error);
+                }
+                throw new DownloaderException($errors);
+            }
+        } catch (\Throwable$exception) {
+            throw new DownloaderException($exception->getMessage(), $exception->getCode(), $exception);
+        }
+    }
+
+    /**
+     * @throws DownloaderException
+     */
+    private function validateResponse(array $arguments, string $app, string $source): void
+    {
+        $this->validate(__DIR__ . DIRECTORY_SEPARATOR .
+            $app . DIRECTORY_SEPARATOR .
+            $source . DIRECTORY_SEPARATOR . 'response.json', $arguments);
+    }
+}
diff --git a/src/DownloaderException.php b/src/DownloaderException.php
new file mode 100644
index 0000000..7a572cc
--- /dev/null
+++ b/src/DownloaderException.php
@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Fykosak\FKSDBDownloaderCore;
+
+class DownloaderException extends \Exception
+{
+}
diff --git a/src/fksdb/GetOrganizers/request.json b/src/fksdb/GetOrganizers/request.json
new file mode 100644
index 0000000..d66acf9
--- /dev/null
+++ b/src/fksdb/GetOrganizers/request.json
@@ -0,0 +1,15 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "type": "object",
+  "required": [
+    "contest_id"
+  ],
+  "properties": {
+    "contest_id": {
+      "type": "integer"
+    },
+    "year": {
+      "type": "integer"
+    }
+  }
+}
diff --git a/src/fksdb/GetOrganizers/response.json b/src/fksdb/GetOrganizers/response.json
new file mode 100644
index 0000000..07bbeac
--- /dev/null
+++ b/src/fksdb/GetOrganizers/response.json
@@ -0,0 +1,78 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "type": "array",
+  "items": {
+    "type": "object",
+    "properties": {
+      "name": {
+        "type": "string"
+      },
+      "personId": {
+        "type": "integer",
+        "min": 0
+      },
+      "email": {
+        "type": [
+          "null",
+          "string"
+        ]
+      },
+      "academicDegreePrefix": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "academicDegreeSuffix": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "career": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "contribution": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "order": {
+        "type": "integer",
+        "min": 0,
+        "max": 10
+      },
+      "role": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "since": {
+        "type": "integer"
+      },
+      "until": {
+        "type": [
+          "integer",
+          "null"
+        ]
+      },
+      "texSignature": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "domainAlias": {
+        "type": [
+          "string",
+          "null"
+        ]
+      }
+    }
+  }
+}
diff --git a/tools/downloader.php b/tools/downloader.php
index 1a884ef..fc0a97c 100644
--- a/tools/downloader.php
+++ b/tools/downloader.php
@@ -2,15 +2,24 @@
 
 declare(strict_types=1);
 
+use Fykosak\FKSDBDownloaderCore\Downloader;
 use Fykosak\FKSDBDownloaderCore\FKSDBDownloader;
-use Fykosak\FKSDBDownloaderCore\Requests\Request;
 
 require_once __DIR__ . '/../vendor/autoload.php';
 require_once __DIR__ . '/pass.php';
 
 $downloader = new FKSDBDownloader(FKSDB_WSDL, FKSDB_USER, FKSDB_PASS, FKSDB_API);
-
-return function (Request $request, bool $soap = true) use ($downloader): ?string {
+$newDownloader = new Downloader([
+    'fksdb' => [
+        'url' => FKSDB_API,
+        'username' => FKSDB_USER,
+        'password' => FKSDB_PASS,
+    ],
+]);
+echo $newDownloader->download('fksdb', 'GetOrganizers', ['contest_id' => 1, 'year' => 37]);
+return $newDownloader;
+/*
+return function (Request $request, bool $soap = true) use ($new): ?string {
     try {
         if ($soap) {
             header('Content-Type: text/xml');
@@ -23,4 +32,4 @@
         var_dump($exception);
     }
     return null;
-};
+};*/