diff --git a/API-Implementation.md b/API-Implementation.md
index 1672c1a..395c823 100644
--- a/API-Implementation.md
+++ b/API-Implementation.md
@@ -5,6 +5,7 @@ The client and the app communicate through several shared-memory message-passing
 ### Messages from client to app
 
 #### process_control_request
+Send individually, as needed.
 ```xml
 <quit/>
 <abort/>
@@ -14,6 +15,7 @@ The client and the app communicate through several shared-memory message-passing
 <network_available/>
 ```
 #### heartbeat
+Sent all together, every 1 sec.
 ```xml
 <heartbeat>
 <wss>
@@ -32,11 +34,14 @@ Not used
 ### Messages from app to client
 
 #### app_status
+Sent together when boinc_report_app_status() called by app
 ```xml
 <current_cpu_time>...
 <checkpoint_cpu_time>...
-<working_set_size>...
 <fraction_done> ...
+[<other_pid>... ]
+[<bytes_sent>...]
+[<bytes_received>...]
 ```
 
 #### trickle_up
@@ -50,6 +55,7 @@ Not used
 Not used
 
 #### graphics_reply
+Sent once, after e.g. ```boinc_web_graphics_url()''' call.
 ```xml
 <web_graphics_url>
 <remote_desktop_addr>