diff --git a/botocore/config.py b/botocore/config.py
index a86e347d77..b5199f9e34 100644
--- a/botocore/config.py
+++ b/botocore/config.py
@@ -224,8 +224,18 @@ class Config:
     :type account_id_endpoint_mode: str
     :param account_id_endpoint_mode: Enables or disables account ID based
         endpoint routing for supported operations.
-
-        Defaults to None.
+        Valid options are:
+
+        * ``preferred`` -- Attempt to resolve account ID during endpoint
+            resolution if supported by the service. If account ID cannot be
+            resolved, fallback to a different endpoint.
+        * ``required`` -- Require account ID to be resolved during endpoint
+            resolution. If account ID cannot be resolved, raises
+            ``AccountIDNotFound`` exception.
+        * ``disabled`` -- Disable account ID based endpoint routing. The SDK
+            will not attempt to resolve account ID during endpoint resolution.
+
+        If not specified, the default behavior is ``preferred``.
     """
 
     OPTION_DEFAULTS = OrderedDict(
diff --git a/botocore/exceptions.py b/botocore/exceptions.py
index e934433bc6..5fcd4a7e23 100644
--- a/botocore/exceptions.py
+++ b/botocore/exceptions.py
@@ -817,4 +817,4 @@ class UnknownEndpointResolutionBuiltInName(EndpointProviderError):
 
 
 class AccountIDNotFound(EndpointResolutionError):
-    fmt = '`account_id_endpoint_mode is set to `required` but no account ID was found.'
+    fmt = '"account_id_endpoint_mode" is set to "required" but no account ID was found.'