diff --git a/ray.go b/ray.go
index 663b2400f..6e55a6e5d 100644
--- a/ray.go
+++ b/ray.go
@@ -21,13 +21,28 @@ func NewRay() *Ray {
 	}
 }
 
+// OutboundRay is a transport interface for outbound connections.
 type OutboundRay interface {
+	// OutboundInput provides a stream for the input of the outbound connection.
+	// The outbound connection shall write all the input until it is closed.
 	OutboundInput() <-chan *alloc.Buffer
+
+	// OutboundOutput provides a stream to retrieve the response from the
+	// outbound connection. The outbound connection shall close the channel
+	// after all responses are receivced and put into the channel.
 	OutboundOutput() chan<- *alloc.Buffer
 }
 
+// InboundRay is a transport interface for inbound connections.
 type InboundRay interface {
+	// InboundInput provides a stream to retrieve the request from client.
+	// The inbound connection shall close the channel after the entire request
+	// is received and put into the channel.
 	InboundInput() chan<- *alloc.Buffer
+
+	// InboudBound provides a stream of data for the inbound connection to write
+	// as response. The inbound connection shall write all the data from the
+	// channel until it is closed.
 	InboundOutput() <-chan *alloc.Buffer
 }