Add tool usage events

src/crewai/utilities/events.py

@@ -0,0 +1,44 @@
+from typing import Any, Callable, Generic, List, Dict, Type, TypeVar
+from functools import wraps
+from pydantic import BaseModel
+
+
+T = TypeVar("T")
+EVT = TypeVar("EVT", bound=BaseModel)
+
+
+class Emitter(Generic[T, EVT]):
+    _listeners: Dict[Type[EVT], List[Callable]] = {}
+
+    def on(self, event_type: Type[EVT]):
+        def decorator(func: Callable):
+            @wraps(func)
+            def wrapper(*args, **kwargs):
+                return func(*args, **kwargs)
+
+            self._listeners.setdefault(event_type, []).append(wrapper)
+            return wrapper
+
+        return decorator
+
+    def emit(self, source: T, event: EVT) -> None:
+        event_type = type(event)
+        for func in self._listeners.get(event_type, []):
+            func(source, event)
+
+
+default_emitter = Emitter[Any, BaseModel]()
+
+
+def emit(source: Any, event: BaseModel, raise_on_error: bool = False) -> None:
+    try:
+        default_emitter.emit(source, event)
+    except Exception as e:
+        if raise_on_error:
+            raise e
+        else:
+            print(f"Error emitting event: {e}")
+
+
+def on(event_type: Type[BaseModel]) -> Callable:
+    return default_emitter.on(event_type)