Add manual endpoint navigation example to MDX setup guide (#1921)

* Update api-playground/mdx-setup.mdx

* Update api-playground/mdx-setup.mdx

* Update api-playground/mdx-setup.mdx

---------

Co-authored-by: mintlify[bot] <109931778+mintlify[bot]@users.noreply.github.com>
Co-authored-by: Ethan Palm <[email protected]>

Author: mintlify[bot]

api-playground/mdx-setup.mdx

@@ -95,7 +95,75 @@ You can manually define API endpoints in individual MDX pages. This approach is
     ```
   </Step>
   <Step title="Add your endpoints to your docs">
-    Add your endpoint pages to the navigation by updating the `pages` field in your `docs.json`. Learn more about structuring your docs in [Navigation](/organize/navigation).
+    Add your endpoint pages to the navigation by updating the `pages` field in your `docs.json`:
+
+    ```json docs.json
+    "navigation": {
+      "tabs": [
+        {
+          "tab": "API Reference",
+          "groups": [
+            {
+              "group": "Users",
+              "pages": [
+                "api-reference/users/create-user",
+                "api-reference/users/get-user",
+                "api-reference/users/update-user"
+              ]
+            },
+            {
+              "group": "Orders",
+              "pages": [
+                "api-reference/orders/create-order",
+                "api-reference/orders/list-orders"
+              ]
+            }
+          ]
+        }
+      ]
+    }
+    ```
+
+    Each page path corresponds to an MDX file in your docs repository. For example, `api-reference/users/create-user.mdx`. Learn more about structuring your docs in [Navigation](/organize/navigation).
+
+    ### Using OpenAPI endpoints in navigation
+
+    If you have an OpenAPI specification, you can reference endpoints directly in your navigation without creating individual MDX files. Reference specific endpoints by including the OpenAPI file path and the endpoint:
+
+    ```json docs.json
+    "navigation": {
+      "pages": [
+        "introduction",
+        "/path/to/users-openapi.json POST /users",
+        "/path/to/orders-openapi.json GET /orders"
+      ]
+    }
+    ```
+
+    You can also set a default OpenAPI spec for a navigation group and reference endpoints by method and path:
+
+    ```json docs.json
+    {
+      "group": "API reference",
+      "openapi": "/path/to/openapi-v1.json",
+      "pages": [
+        "overview",
+        "authentication",
+        "GET /users",
+        "POST /users",
+        {
+          "group": "Orders",
+          "openapi": "/path/to/openapi-v2.json",
+          "pages": [
+            "GET /orders",
+            "POST /orders"
+          ]
+        }
+      ]
+    }
+    ```
+
+    For more details on OpenAPI integration, see [OpenAPI setup](/api-playground/openapi-setup).
   </Step>
 </Steps>