api documentation wrote for bmi calculator

api-documentation.md

@@ -1,3 +1,41 @@
 #Daily diet api documentation
 
-##v1.0
+##v1.0
+
+### `/calculate/bmi`
+method: `POST`
+
+*input*: 
+- height in centimiters
+- weight in kilograms
+```json
+{
+	"height":180,  
+	"weight":80
+}
+```
+
+*output*:
+- `bmi_value` rounded up to 2 decimal points
+- `bmi_status` one of **Underweight**, **Normal weight**, **Overweight** and **Obesity**
+```json
+{
+  "bmi_status": "Normal weight", 
+  "bmi_value": 24.69
+}
+
+```
+
+*in case of errors*: response code will be **400**
+```json
+{
+    "errors": {
+        "height": [
+            "This field is required."
+        ],
+        "weight": [
+            "This field is required."
+        ]
+    }
+}
+```