diff --git a/README.md b/README.md
index d1670ac..6bdba8f 100644
--- a/README.md
+++ b/README.md
@@ -76,20 +76,24 @@ The TFW message format:
 
 ```text
 {
-    "key: "some identifier used for addressing",
+    "key: ...some identifier used for addressing...,
     "data":
     {
         ...
         JSON object carrying anything, preferably cats
         ...
     },
-    "trigger": "FSM action"
+    "trigger": ...FSM action...,
+    "signature": ...HMAC signature for authenticated messages...,
+    "seq": ...sequence number...
 }
 ```
 
 - The `key` field is used by TFW for addressing and every message must have one (it can be an empty string though)
 - The `data` object can contain anything you might want to send
 - The `trigger` key is an optional field that triggers an FSM action with that name from the current state (whatever that might be)
+- The `signature` field is present on authenticated messages (such as `fsm_update`s)
+- The `seq` key is a counter incremented with each proxied message in the TFW server
 
 To mirror messages back to their sources you can use a special messaging format, in which the message to be mirrored is enveloped inside the `data` field of the outer message: