diff --git a/application/Espo/Controllers/ApiIndex.php b/application/Espo/Controllers/ApiIndex.php
new file mode 100644
index 0000000000..308cd49e2b
--- /dev/null
+++ b/application/Espo/Controllers/ApiIndex.php
@@ -0,0 +1,38 @@
+<?php
+/************************************************************************
+ * This file is part of EspoCRM.
+ *
+ * EspoCRM - Open Source CRM application.
+ * Copyright (C) 2014-2020 Yuri Kuznetsov, Taras Machyshyn, Oleksiy Avramenko
+ * Website: https://www.espocrm.com
+ *
+ * EspoCRM is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * EspoCRM is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with EspoCRM. If not, see http://www.gnu.org/licenses/.
+ *
+ * The interactive user interfaces in modified source and object code versions
+ * of this program must display Appropriate Legal Notices, as required under
+ * Section 5 of the GNU General Public License version 3.
+ *
+ * In accordance with Section 7(b) of the GNU General Public License version 3,
+ * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
+ ************************************************************************/
+
+namespace Espo\Controllers;
+
+class ApiIndex {
+
+    public function getActionIndex()
+    {
+        return "EspoCRM REST API";
+    }
+}
diff --git a/application/Espo/Core/Utils/Api/Auth.php b/application/Espo/Core/Api/Auth.php
similarity index 99%
rename from application/Espo/Core/Utils/Api/Auth.php
rename to application/Espo/Core/Api/Auth.php
index 407673cc94..852648e85c 100644
--- a/application/Espo/Core/Utils/Api/Auth.php
+++ b/application/Espo/Core/Api/Auth.php
@@ -27,7 +27,7 @@
  * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
  ************************************************************************/
 
-namespace Espo\Core\Utils\Api;
+namespace Espo\Core\Api;
 
 use Espo\Core\Utils\Auth as AuthUtil;
 
diff --git a/application/Espo/Core/Utils/Api/Output.php b/application/Espo/Core/Api/Output.php
similarity index 94%
rename from application/Espo/Core/Utils/Api/Output.php
rename to application/Espo/Core/Api/Output.php
index e8f148305d..7beadb41dd 100644
--- a/application/Espo/Core/Utils/Api/Output.php
+++ b/application/Espo/Core/Api/Output.php
@@ -27,7 +27,7 @@
  * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
  ************************************************************************/
 
-namespace Espo\Core\Utils\Api;
+namespace Espo\Core\Api;
 
 use Psr\Http\Message\{
     ResponseInterface as Response,
@@ -62,15 +62,14 @@ class Output
 
     public function render(Response $response, $data = null) : Response
     {
-        if (is_array($data)) {
-            $dataArr = array_values($data);
-            $data = empty($dataArr[0]) ? false : $dataArr[0];
-        } else if ($data instanceof \StdClass) {
-            $data = json_encode($data);
+        if (is_string($data)) {
+            $response->getBody()->write($data);
+        } else {
+            if ($data) {
+                $response->setBody($data);
+            }
         }
 
-        $response->getBody()->write($data);
-
         return $response;
     }
 
diff --git a/application/Espo/Core/Api/Request.php b/application/Espo/Core/Api/Request.php
new file mode 100644
index 0000000000..89e0bac6da
--- /dev/null
+++ b/application/Espo/Core/Api/Request.php
@@ -0,0 +1,48 @@
+<?php
+/************************************************************************
+ * This file is part of EspoCRM.
+ *
+ * EspoCRM - Open Source CRM application.
+ * Copyright (C) 2014-2020 Yuri Kuznetsov, Taras Machyshyn, Oleksiy Avramenko
+ * Website: https://www.espocrm.com
+ *
+ * EspoCRM is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * EspoCRM is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with EspoCRM. If not, see http://www.gnu.org/licenses/.
+ *
+ * The interactive user interfaces in modified source and object code versions
+ * of this program must display Appropriate Legal Notices, as required under
+ * Section 5 of the GNU General Public License version 3.
+ *
+ * In accordance with Section 7(b) of the GNU General Public License version 3,
+ * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
+ ************************************************************************/
+
+namespace Espo\Core\Api;
+
+interface Request
+{
+    /**
+     * Get a query parameter.
+     */
+    public function get(string $name) : ?string;
+
+    /**
+     * Get a header value.
+     */
+    public function getHeader(string $name) : ?string;
+
+    /**
+     * Get a request method.
+     */
+    public function getMethod() : string;
+}
diff --git a/application/Espo/Core/Utils/Api/RequestWrapper.php b/application/Espo/Core/Api/RequestWrapper.php
similarity index 88%
rename from application/Espo/Core/Utils/Api/RequestWrapper.php
rename to application/Espo/Core/Api/RequestWrapper.php
index 91d1bd95f6..0c11978d14 100644
--- a/application/Espo/Core/Utils/Api/RequestWrapper.php
+++ b/application/Espo/Core/Api/RequestWrapper.php
@@ -27,17 +27,19 @@
  * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
  ************************************************************************/
 
-namespace Espo\Core\Utils\Api;
+namespace Espo\Core\Api;
 
 use Psr\Http\Message\{
-    ServerRequestInterface as Request,
+    ServerRequestInterface as Psr7Request,
 };
 
-class RequestWrapper
+use Espo\Core\Api\Request as ApiRequest;
+
+class RequestWrapper implements ApiRequest
 {
     protected $request;
 
-    public function __construct(Request $request)
+    public function __construct(Psr7Request $request)
     {
         $this->request = $request;
     }
@@ -54,7 +56,7 @@ class RequestWrapper
         return $this->request->getHeaderLine($name);
     }
 
-    public function getMethod()
+    public function getMethod() : string
     {
         return $this->request->getMethod();
     }
diff --git a/application/Espo/Core/Api/Response.php b/application/Espo/Core/Api/Response.php
new file mode 100644
index 0000000000..4ec684c90b
--- /dev/null
+++ b/application/Espo/Core/Api/Response.php
@@ -0,0 +1,52 @@
+<?php
+/************************************************************************
+ * This file is part of EspoCRM.
+ *
+ * EspoCRM - Open Source CRM application.
+ * Copyright (C) 2014-2020 Yuri Kuznetsov, Taras Machyshyn, Oleksiy Avramenko
+ * Website: https://www.espocrm.com
+ *
+ * EspoCRM is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * EspoCRM is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with EspoCRM. If not, see http://www.gnu.org/licenses/.
+ *
+ * The interactive user interfaces in modified source and object code versions
+ * of this program must display Appropriate Legal Notices, as required under
+ * Section 5 of the GNU General Public License version 3.
+ *
+ * In accordance with Section 7(b) of the GNU General Public License version 3,
+ * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
+ ************************************************************************/
+
+namespace Espo\Core\Api;
+
+use Psr\Http\Message\{
+    ResponseInterface as Psr7Response,
+};
+
+interface Response
+{
+    /**
+     * Set a status code.
+     */
+    public function setStatus(int $code, ?string $reason);
+
+    /**
+     * Set a specific header.
+     */
+    public function setHeader(string $name, string $value);
+
+    /**
+     * Get a result psr7 response.
+     */
+    public function getResponse() : Psr7Response;
+}
diff --git a/application/Espo/Core/Utils/Api/ResponseWrapper.php b/application/Espo/Core/Api/ResponseWrapper.php
similarity index 87%
rename from application/Espo/Core/Utils/Api/ResponseWrapper.php
rename to application/Espo/Core/Api/ResponseWrapper.php
index e5541d1d84..b1d25c8f30 100644
--- a/application/Espo/Core/Utils/Api/ResponseWrapper.php
+++ b/application/Espo/Core/Api/ResponseWrapper.php
@@ -27,17 +27,19 @@
  * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
  ************************************************************************/
 
-namespace Espo\Core\Utils\Api;
+namespace Espo\Core\Api;
 
 use Psr\Http\Message\{
-    ResponseInterface as Response,
+    ResponseInterface as Psr7Response,
 };
 
-class ResponseWrapper
+use Espo\Core\Api\Response as ApiResponse;
+
+class ResponseWrapper implements ApiResponse
 {
     protected $response;
 
-    public function __construct(Response $response)
+    public function __construct(Psr7Response $response)
     {
         $this->response = $response;
     }
@@ -52,7 +54,7 @@ class ResponseWrapper
         $this->response = $this->response->withHeader($name, $value);
     }
 
-    public function getResponse() : Response
+    public function getResponse() : Psr7Response
     {
         return $this->response;
     }
diff --git a/application/Espo/Core/Utils/Api/Slim.php b/application/Espo/Core/Api/Slim.php
similarity index 100%
rename from application/Espo/Core/Utils/Api/Slim.php
rename to application/Espo/Core/Api/Slim.php
diff --git a/application/Espo/Core/Application.php b/application/Espo/Core/Application.php
index fb4090a751..cf45d94009 100644
--- a/application/Espo/Core/Application.php
+++ b/application/Espo/Core/Application.php
@@ -38,10 +38,10 @@ use Espo\Core\{
     EntryPointManager,
     CronManager,
     Utils\Auth,
-    Utils\Api\Auth as ApiAuth,
-    Utils\Api\Output as ApiOutput,
-    Utils\Api\RequestWrapper,
-    Utils\Api\ResponseWrapper,
+    Api\Auth as ApiAuth,
+    Api\Output as ApiOutput,
+    Api\RequestWrapper,
+    Api\ResponseWrapper,
     Utils\Route,
     Utils\Autoload,
     Portal\Application as PortalApplication,
@@ -420,7 +420,6 @@ class Application
                         $conditions = $route['conditions'] ?? [];
                         if (($conditions['auth'] ?? true) === false) {
                             $authRequired = false;
-
                         }
 
                         $auth = $this->createAuth($request);
@@ -454,16 +453,26 @@ class Application
 
         $paramKeys = array_keys($route['params']);
 
+        $setKeyList = [];
+
         foreach ($paramKeys as $key) {
+            $value = $route['params'][$key];
+
             $paramName = $key;
-              if ($key[0] === ':') {
-                $paramName = substr($key, 1);
-                $params[$paramName] = $args[$paramName];
+            if ($value[0] === ':') {
+                $realKey = substr($value, 1);
+                $params[$paramName] = $args[$realKey];
+                $setKeyList[] = $realKey;
             } else {
-                $params[$paramName] = $route['params'][$key];
+                $params[$paramName] = $value;
             }
         }
 
+        foreach ($args as $key => $value) {
+            if (in_array($key, $setKeyList)) continue;
+            $params[$key] = $value;
+        }
+
         $controllerName = $params['controller'] ?? $args['controller'] ?? null;
         $actionName = $params['action'] ?? $args['action'] ?? null;
 
diff --git a/application/Espo/Core/ControllerManager.php b/application/Espo/Core/ControllerManager.php
index 39ab0e6bd8..209c6e9ab0 100644
--- a/application/Espo/Core/ControllerManager.php
+++ b/application/Espo/Core/ControllerManager.php
@@ -37,6 +37,8 @@ use Espo\Core\{
     Utils\ClassFinder,
     Utils\Json,
     Utils\Util,
+    Api\Request,
+    Api\Response,
 };
 
 class ControllerManager
@@ -54,8 +56,14 @@ class ControllerManager
         $this->controllersHash = (object) [];
     }
 
-    public function process(string $controllerName, string $actionName, $params, $data, $request, $response = null)
-    {
+    public function process(
+        string $controllerName,
+        string $actionName,
+        array $params,
+        $data,
+        Request $request,
+        Response $response
+    ) {
         $controller = $this->getController($controllerName);
         return $this->processRequest($controller, $controllerName, $actionName, $params, $data, $request, $response);
     }
@@ -95,7 +103,13 @@ class ControllerManager
     }
 
     protected function processRequest(
-        object $controller, string $controllerName, string $actionName, $params, $data, $request, $response = null
+        object $controller,
+        string $controllerName,
+        string $actionName,
+        array $params,
+        $data,
+        Request $request,
+        Response $response
     ) {
         if ($data && stristr($request->getContentType(), 'application/json')) {
             $data = json_decode($data);
diff --git a/application/Espo/Resources/routes.json b/application/Espo/Resources/routes.json
index 66759c8c81..38722f5eba 100644
--- a/application/Espo/Resources/routes.json
+++ b/application/Espo/Resources/routes.json
@@ -2,7 +2,10 @@
     {
         "route": "/",
         "method": "get",
-        "params": "\"EspoCRM REST API\""
+        "params": {
+            "controller": "ApiIndex",
+            "action": "index"
+        }
     },
     {
         "route": "/App/user",