diff --git a/src/agents/guardrail.py b/src/agents/guardrail.py
index a96f0f7d7..d2ce79400 100644
--- a/src/agents/guardrail.py
+++ b/src/agents/guardrail.py
@@ -109,7 +109,9 @@ async def run(
         context: RunContextWrapper[TContext],
     ) -> InputGuardrailResult:
         if not callable(self.guardrail_function):
-            raise UserError(f"Guardrail function must be callable, got {self.guardrail_function}")
+            raise UserError(
+                f"Guardrail function must be callable, got {self.guardrail_function}"
+            )
 
         output = self.guardrail_function(context, agent, input)
         if inspect.isawaitable(output):
@@ -160,7 +162,9 @@ async def run(
         self, context: RunContextWrapper[TContext], agent: Agent[Any], agent_output: Any
     ) -> OutputGuardrailResult:
         if not callable(self.guardrail_function):
-            raise UserError(f"Guardrail function must be callable, got {self.guardrail_function}")
+            raise UserError(
+                f"Guardrail function must be callable, got {self.guardrail_function}"
+            )
 
         output = self.guardrail_function(context, agent, agent_output)
         if inspect.isawaitable(output):
@@ -183,11 +187,19 @@ async def run(
 
 # For InputGuardrail
 _InputGuardrailFuncSync = Callable[
-    [RunContextWrapper[TContext_co], "Agent[Any]", Union[str, list[TResponseInputItem]]],
+    [
+        RunContextWrapper[TContext_co],
+        "Agent[Any]",
+        Union[str, list[TResponseInputItem]],
+    ],
     GuardrailFunctionOutput,
 ]
 _InputGuardrailFuncAsync = Callable[
-    [RunContextWrapper[TContext_co], "Agent[Any]", Union[str, list[TResponseInputItem]]],
+    [
+        RunContextWrapper[TContext_co],
+        "Agent[Any]",
+        Union[str, list[TResponseInputItem]],
+    ],
     Awaitable[GuardrailFunctionOutput],
 ]
 
@@ -215,9 +227,11 @@ def input_guardrail(
 
 
 def input_guardrail(
-    func: _InputGuardrailFuncSync[TContext_co]
-    | _InputGuardrailFuncAsync[TContext_co]
-    | None = None,
+    func: (
+        _InputGuardrailFuncSync[TContext_co]
+        | _InputGuardrailFuncAsync[TContext_co]
+        | None
+    ) = None,
     *,
     name: str | None = None,
 ) -> (
@@ -284,15 +298,20 @@ def output_guardrail(
 
 
 def output_guardrail(
-    func: _OutputGuardrailFuncSync[TContext_co]
-    | _OutputGuardrailFuncAsync[TContext_co]
-    | None = None,
+    func: (
+        _OutputGuardrailFuncSync[TContext_co]
+        | _OutputGuardrailFuncAsync[TContext_co]
+        | None
+    ) = None,
     *,
     name: str | None = None,
 ) -> (
     OutputGuardrail[TContext_co]
     | Callable[
-        [_OutputGuardrailFuncSync[TContext_co] | _OutputGuardrailFuncAsync[TContext_co]],
+        [
+            _OutputGuardrailFuncSync[TContext_co]
+            | _OutputGuardrailFuncAsync[TContext_co]
+        ],
         OutputGuardrail[TContext_co],
     ]
 ):
@@ -308,9 +327,17 @@ async def my_async_guardrail(...): ...
     """
 
     def decorator(
-        f: _OutputGuardrailFuncSync[TContext_co] | _OutputGuardrailFuncAsync[TContext_co],
+        f: (
+            _OutputGuardrailFuncSync[TContext_co]
+            | _OutputGuardrailFuncAsync[TContext_co]
+        ),
     ) -> OutputGuardrail[TContext_co]:
-        return OutputGuardrail(guardrail_function=f, name=name)
+        
+        return OutputGuardrail(
+            guardrail_function=f, 
+            # Guardrail name defaults to function name when not specified (None).
+            name=name if name else f.__name__
+        )
 
     if func is not None:
         # Decorator was used without parentheses