diff --git a/src/xai_sdk/auth.py b/src/xai_sdk/auth.py
index 33551a8..5f2f28b 100644
--- a/src/xai_sdk/auth.py
+++ b/src/xai_sdk/auth.py
@@ -1,3 +1,9 @@
+"""Authentication client module for xAI SDK.
+
+This module provides clients for interacting with the xAI Authentication API,
+supporting both synchronous and asynchronous gRPC channels.
+"""
+
 from typing import Union
 
 import grpc
@@ -6,10 +12,45 @@
 
 
 class BaseClient:
-    """Base Client for interacting with `Auth` API."""
+    """Base client for interacting with the xAI Authentication API.
+
+    This class serves as the foundation for authentication-related operations
+    in the xAI SDK. It manages the underlying gRPC stub used to communicate
+    with the authentication service.
+
+    Attributes:
+        _stub: The gRPC stub for communicating with the Auth API service.
+    """
 
     _stub: auth_pb2_grpc.AuthStub
 
-    def __init__(self, channel: Union[grpc.Channel, grpc.aio.Channel]):
-        """Creates a new client based on a gRPC channel."""
+    def __init__(self, channel: Union[grpc.Channel, grpc.aio.Channel]) -> None:
+        """Initialize a new Auth API client.
+
+        Creates a new client instance with the provided gRPC channel. The channel
+        can be either a synchronous (grpc.Channel) or asynchronous (grpc.aio.Channel)
+        channel, allowing for flexible usage patterns.
+
+        Args:
+            channel: A gRPC channel (sync or async) for communicating with the service.
+                    Must be properly configured and connected before use.
+
+        Raises:
+            TypeError: If the channel is not a valid gRPC channel type.
+
+        Example:
+            ```
+            import grpc
+            from xai_sdk.auth import BaseClient
+
+            # Create a synchronous channel
+            channel = grpc.insecure_channel("api.xai.com:50051")
+            client = BaseClient(channel)
+            ```
+        """
+        if not isinstance(channel, (grpc.Channel, grpc.aio.Channel)):
+            raise TypeError(
+                f"channel must be a grpc.Channel or grpc.aio.Channel, "
+                f"got {type(channel).__name__}"
+            )
         self._stub = auth_pb2_grpc.AuthStub(channel)