diff --git a/message/message.go b/message/message.go
index 45bf180a..e94121bb 100644
--- a/message/message.go
+++ b/message/message.go
@@ -62,10 +62,14 @@ func NewText(text string) *Message {
 	return New(&TextContent{Text: text})
 }
 
+// String implements fmt.Stringer, returning the concatenated text of all
+// TextContent in the message (delegating to Contents.Text).
 func (m *Message) String() string {
 	return m.Contents.Text()
 }
 
+// Usage returns the aggregated UsageDetails carried by the message's
+// UsageContent (delegating to Contents.Usage).
 func (m *Message) Usage() UsageDetails {
 	return m.Contents.Usage()
 }