diff --git a/include/ircd/m/sync/data.h b/include/ircd/m/sync/data.h
index 4f3453f9d..8bdd6c914 100644
--- a/include/ircd/m/sync/data.h
+++ b/include/ircd/m/sync/data.h
@@ -52,29 +52,55 @@ struct ircd::m::sync::data
 
 	/// The client. This may be null if sync is being called internally.
 	ircd::client *client {nullptr};
+
+	/// Parsed arguments for the request.
 	const sync::args *args {nullptr};
 
-	// User related
+	/// User apropos.
 	const m::user user;
+
+	/// User's room convenience.
 	const m::user::room user_room;
+
+	/// User's room state convenience.
 	const m::room::state user_state;
+
+	/// User's rooms interface convenience.
 	const m::user::rooms user_rooms;
+
+	/// Buffer for supplied or fetched filter.
 	const std::string filter_buf;
+
+	/// Structured parse of the above filter.
 	const m::filter filter;
+
+	/// User's device ID from the access token.
 	const device::id device_id;
 
+	/// Event apropos (may be null for polylog).
+	const m::event *event {nullptr};
+
+	/// Event room's interface convenience.
+	const m::room *room {nullptr};
+
+	/// User's membership in event's room.
+	string_view membership;
+
+	/// Event's depth in room.
+	int64_t room_depth {0}; // if *room
+
+	/// Event room's top-head sequence number
+	event::idx room_head {0}; // if *room
+
+	/// Event's sequence number
+	event::idx event_idx {0}; // if *event
+
+	/// Client transaction_id apropos
+	string_view client_txnid;
+
 	/// The json::stack master object
 	json::stack *out {nullptr};
 
-	// apropos contextual
-	const m::event *event {nullptr};
-	const m::room *room {nullptr};
-	string_view membership;
-	int64_t room_depth {0}; // if *room
-	event::idx room_head {0}; // if *room
-	event::idx event_idx {0}; // if *event
-	string_view client_txnid;
-
 	data(const m::user &user,
 	     const m::events::range &range,
 	     ircd::client *const &client = nullptr,
diff --git a/matrix/sync.cc b/matrix/sync.cc
index f59ff93ba..91bbf51ab 100644
--- a/matrix/sync.cc
+++ b/matrix/sync.cc
@@ -111,13 +111,16 @@ ircd::m::sync::make_since(const string_view &input)
 			0UL
 	};
 
+	// prefix
 	assert(!part[0] || part[0] == "ctor");
 	return
 	{
+		// since
 		part[1]?
 			lex_cast<event::idx>(part[1]):
 			0UL,
 
+		// snapshot
 		part[2]?
 			lex_cast<event::idx>(part[2]):
 			0UL,