fix Function tool webhook example

Author: stephenvapiai

fern/tools/custom-tools.mdx

@@ -188,25 +188,30 @@ When your server receives a tool call request from Vapi, it will be in the follo
         "toolCallList": [
             {
                 "id": "toolu_01DTPAzUm5Gk3zxrpJ969oMF",
-                "name": "get_weather",
-                "arguments": {
-                    "location": "San Francisco"
+                "type": "function",
+                "function": {
+                    "name": "get_weather",
+                    "arguments": {
+                        "location": "San Francisco"
+                    }
                 }
             }
         ],
         "toolWithToolCallList": [
             {
                 "type": "function",
-                "name": "get_weather",
-                "parameters": {
-                    "type": "object",
-                    "properties": {
-                        "location": {
-                            "type": "string"
+                "function": {
+                    "name": "get_weather",
+                    "parameters": {
+                        "type": "object",
+                        "properties": {
+                            "location": {
+                                "type": "string"
+                            }
                         }
-                    }
+                    },
+                    "description": "Retrieves the current weather for a specified location"
                 },
-                "description": "Retrieves the current weather for a specified location",
                 "server": {
                     "url": "https://api.openweathermap.org/data/2.5/weather"
                 },
@@ -216,7 +221,7 @@ When your server receives a tool call request from Vapi, it will be in the follo
                     "type": "function",
                     "function": {
                         "name": "get_weather",
-                        "parameters": {
+                        "arguments": {
                             "location": "San Francisco"
                         }
                     }