diff --git a/controllers/OpenApiController.php b/controllers/OpenApiController.php
new file mode 100644
index 0000000..e6a5001
--- /dev/null
+++ b/controllers/OpenApiController.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace app\controllers;
+
+class OpenApiController extends \yii\web\Controller
+{
+    public function actionIndex()
+    {
+        return $this->render('index');
+    }
+
+}
diff --git a/views/open-api/index.php b/views/open-api/index.php
new file mode 100644
index 0000000..9e501ac
--- /dev/null
+++ b/views/open-api/index.php
@@ -0,0 +1,20 @@
+<?php
+
+/** @var yii\web\View $this */
+
+$this->title = 'OpenAPI spec';
+$this->registerJsFile('//unpkg.com/swagger-ui-dist/swagger-ui-bundle.js');
+$this->registerCssFile('//unpkg.com/swagger-ui-dist/swagger-ui.css');
+
+$loader = <<< JS
+    const ui = SwaggerUIBundle({
+        url: '/openapi.yml',
+        dom_id: '#swagger-ui'
+    });
+JS;
+$this->registerJs($loader, \yii\web\View::POS_END);
+
+?>
+
+<noscript>You need to enable JS to load Swagger UI</noscript>
+<div id="swagger-ui"></div>
diff --git a/web/openapi.yml b/web/openapi.yml
new file mode 100644
index 0000000..9a0c288
--- /dev/null
+++ b/web/openapi.yml
@@ -0,0 +1,87 @@
+info:
+  title: Parameters API
+  version: '1.0'
+openapi: '3.1.0'
+tags:
+  - name: Routes
+paths:
+  /api/list:
+    get:
+      tags:
+        - Routes
+      summary: Get all parameters
+      description: Get all parameters
+      responses:
+        200:
+          description: OK
+          content:
+            application/json:
+              schema:
+                type: array
+                items:
+                  $ref: '#/components/schemas/Parameter'
+                example: [
+                  {
+                    "id": 0,
+                    "title": "A thing happening somewhere",
+                    "type": 1,
+                    "icons": null
+                  },
+                  {
+                    "id": 2,
+                    "title": "The fox jumping over a cat",
+                    "type": 1,
+                    "icons": {
+                      "icon": {
+                        "original_name": "fox_jump.jpeg",
+                        "url": "/images/SHA256_HASH.jpeg",
+                        "sha256": "SHA256"
+                      },
+                      "icon_gray": {
+                        "original_name": "fox_jump.gray.jpeg",
+                        "url": "/images/SHA256_HASH.jpeg",
+                        "sha256": "SHA256"
+                      }
+                    }
+                  }
+                ]
+components:
+  schemas:
+    Image:
+      type: object
+      properties:
+        source_name:
+          type: string
+          example: "source_file.jpeg"
+        url:
+          type: string
+          example: "/images/SHA256_HASH.jpeg"
+        sha256:
+          type: string
+      required:
+        - source_name
+        - url
+        - example
+    Parameter:
+      type: object
+      properties:
+        id:
+          type: number
+          example: 0
+        title:
+          type: string
+          example: 'A quick brown fox jumping over a lazy cat'
+        type:
+          type: number
+          example: 0
+        icons:
+          type: object
+          properties:
+            icon:
+              $ref: '#/components/schemas/Image'
+            icon_gray:
+              $ref: '#/components/schemas/Image'
+      required:
+        - id
+        - title
+        - type
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