Clarify usage of transport hints

index.bs

@@ -872,16 +872,21 @@ these methods.
 </pre>
 
 <div dfn-for="Transport">
-    This enumeration defines the valid transports over which a client might
-    look for an Authenticator that can provide an assertion for the respective
-    credential.  Note that these are a hint from the Relying Party to the
-    client as to its best belief of how an authenticator may be reached.
+    Non-platform Authenticators communicate with Clients using a variety of
+    transports.  This enumaration defines a hint as to how Clients might
+    communicate with a particular Authenticator in order to obtain an assertion
+    for a specific credential.  Note that these hints represent the [RP]'s best
+    belief as to how an Authenticator may be reached.  A [RP] may obtain a list
+    of transports hints from some attestation formats or via some out-of-band
+    mechanism; it is outside the scope of this specification to define that
+    mechanism.
+
     <ul>
-        <li><dfn>usb</dfn> - the respective authenticator may be contacted over
+        <li><dfn>usb</dfn> - the respective Authenticator may be contacted over
             USB.
-        <li><dfn>nfc</dfn> - the respective authenticator may be contacted over
+        <li><dfn>nfc</dfn> - the respective Authenticator may be contacted over
             Near Field Communication (NFC).
-        <li><dfn>ble</dfn> - the respective authenticator may be contacted over
+        <li><dfn>ble</dfn> - the respective Authenticator may be contacted over
             Bluetooth Smart (Bluetooth Low Energy / BLE).
     </ul>
 <div>