toString doc

doc/api.md

@@ -15,7 +15,7 @@ Content-Type: application/json
 
 ---
 
-## 1️⃣ POST `/sort`
+## POST `/sort`
 
 Sorts an array (numeric or alphabetical) and returns the sorted array.
 
@@ -45,7 +45,7 @@ POST /sort
 ```
 
 
-## 2️⃣ POST `/isOdd`
+## POST `/isOdd`
 
 Checks if a given number is odd.
 
@@ -75,7 +75,7 @@ POST /isOdd
 
 ---
 
-## 3️⃣ POST `/isEven`
+## POST `/isEven`
 
 Checks if a given number is even.
 
@@ -103,6 +103,34 @@ POST /isEven
 }
 ```
 
+## POST `/toString`
+
+calls .toString()
+
+### Request
+
+**URL:**
+
+```
+POST /toString
+```
+
+**Body Example:**
+
+```json
+{
+  "number": 7
+}
+```
+
+### Successful Response
+
+```json
+{
+  "ret": "7"
+}
+```
+
 ## 📌 Example Usage with `curl`
 
 ### Sort an array (Linux/macOS)