diff --git a/priv/emqx.schema b/priv/emqx.schema
index 6ee8fb71c..c893d0521 100644
--- a/priv/emqx.schema
+++ b/priv/emqx.schema
@@ -852,10 +852,17 @@ end}.
   {datatype, string}
 ]}.
 
+%% @doc Specify a module that defines the `enrich_clientid_alias/2'
+%% function.  This function will be used to enrich the client/channel
+%% information with clientid and/or common name aliases (or other
+%% enrichments the module may implement).
 {mapping, "clientid_enrichment_module", "emqx.clientid_enrichment_module", [
   {datatype, atom}
 ]}.
 
+%% @doc Specify a module that defines the `check_authn/2' function.
+%% This function will be used in the `client.authenticate' hook as a
+%% way to implement custom authentication logic.
 {mapping, "special_auth_module", "emqx.special_auth_module", [
   {datatype, atom}
 ]}.