@@ -83,9 +83,22 @@ The greeting message format is:
2.2.1 Capabilities
------------------
-As of the date this document was last revised, no server or client
-capability strings have been defined.
+- "async"
+If both the server and the client have the "async" capability, then
+the client is allowed to send async commands. An async command is a
+regular command with the "id" member mandatory (see 2.3), but the
+response may be delayed.
+
+The client must match the incoming responses with the "id" member
+associated with the command.
+
+The client is allowed to make requests while previous requests are
+pending. The responses may come out of order.
+
+When a client is disconnected, the pending commands are not
+necessarily cancelled. However, future clients will not get replies
+from commands they didn't make.
2.3 Issuing Commands
--------------------