diff --git a/docs/config.qmd b/docs/config.qmd
index 6414b63a5..0e49d1992 100644
--- a/docs/config.qmd
+++ b/docs/config.qmd
@@ -165,7 +165,9 @@ datasets:
       content: value
       # ...
 
-    # Optional[Dict[str, List]]. Roles mapping in the messages. The default is:
+    # Optional[Dict[str, List]]. Roles mapping in the messages.
+    # The format is {target_role: [source_roles]}. All source roles will be mapped to the target role.
+    # The default is:
     roles:
       user: ["human", "user"]
       assistant: ["gpt", "assistant"]