diff --git a/haystack/utils/callable_serialization.py b/haystack/utils/callable_serialization.py
index e919f61499..f2f83a768c 100644
--- a/haystack/utils/callable_serialization.py
+++ b/haystack/utils/callable_serialization.py
@@ -8,6 +8,7 @@
 def serialize_callable(callable_handle: Callable) -> str:
     """
     Serializes a callable to its full path.
+
     :param callable_handle: The callable to serialize
     :return: The full path of the callable
     """
@@ -24,6 +25,7 @@ def serialize_callable(callable_handle: Callable) -> str:
 def deserialize_callable(callable_handle: str) -> Optional[Callable]:
     """
     Deserializes a callable given its full import path as a string.
+
     :param callable_handle: The full path of the callable_handle
     :return: The callable
     :raises DeserializationError: If the callable cannot be found
diff --git a/haystack/utils/hf.py b/haystack/utils/hf.py
index b941a742f0..60cc474457 100644
--- a/haystack/utils/hf.py
+++ b/haystack/utils/hf.py
@@ -40,6 +40,13 @@ def __str__(self):
 
     @staticmethod
     def from_str(string: str) -> "HFGenerationAPIType":
+        """
+        Convert a string to a HFGenerationAPIType enum.
+
+        :param string: The string to convert.
+        :return: The corresponding HFGenerationAPIType enum.
+
+        """
         enum_map = {e.value: e for e in HFGenerationAPIType}
         mode = enum_map.get(string)
         if mode is None:
diff --git a/haystack/utils/url_validation.py b/haystack/utils/url_validation.py
index 6d4c9e69d5..7770288de1 100644
--- a/haystack/utils/url_validation.py
+++ b/haystack/utils/url_validation.py
@@ -1,6 +1,7 @@
 from urllib.parse import urlparse
 
 
-def is_valid_http_url(url) -> bool:
+def is_valid_http_url(url: str) -> bool:
+    """Check if a URL is a valid HTTP/HTTPS URL."""
     r = urlparse(url)
     return all([r.scheme in ["http", "https"], r.netloc])