added a calculus function

app.py

@@ -18,6 +18,26 @@ def my_custom_tool(arg1:str, arg2:int)-> str: #it's import to specify the return
     """
     return "What magic will you build ?"
 
+
+@tool
+def calculus(arg1:char, arg2:double, arg3: double)-> double:
+    """A tool that does basic math operations, like adition, substraction, multimplication and division between two real numbers. 
+    Args:
+        arg1: the operator (should be one of the following: '+','-','*','/')
+        arg2: the first number
+        arg3: the second number
+    """
+    if char=='+'
+        return arg2+arg3
+    else if char=='-'
+        return arg2-arg3
+    else if char=='*'
+        return arg2*arg3
+    else if char=='/'
+        return arg2/arg3
+    
+    return "The character in arg1 wasn't a valid mathematical operation!"
+
 @tool
 def get_current_time_in_timezone(timezone: str) -> str:
     """A tool that fetches the current local time in a specified timezone.