diff --git a/go/catalogue/engine_seat.go b/go/catalogue/engine_seat.go
index 71a8afd..b3b695b 100644
--- a/go/catalogue/engine_seat.go
+++ b/go/catalogue/engine_seat.go
@@ -42,7 +42,7 @@ func EngineVerbs() []Verb {
 		{Name: "acts", Description: "Every act this machine's engine was asked through this seat (novox/hq ADR 0563 §9): " +
 			"each hand-over, access act and setuid search, open, done or refused, with who asked, the ask and the " +
 			"operator's warrant. Read-only.",
-			Input: schema(map[string]string{"limit": "at most this many, newest"}, nil)},
+			Input: schema(map[string]string{"limit": "at most this many, newest", "id": "one act, by its id"}, nil)},
 	}
 }
 
diff --git a/go/catalogue/seats_test.go b/go/catalogue/seats_test.go
index 79036d6..9113bd7 100644
--- a/go/catalogue/seats_test.go
+++ b/go/catalogue/seats_test.go
@@ -73,6 +73,10 @@ func TestTheSeatsAreAClosedSetAndEachNamesItsDecision(t *testing.T) {
 		for _, v := range engine.Serves {
 			verbs = append(verbs, v.Name)
 		}
+		// acts reads one act by its id too (ADR 0563 §9: the seat's tools are its command line).
+		if props, _ := engine.Serves[len(engine.Serves)-1].Input["properties"].(map[string]any); props["id"] == nil {
+			t.Errorf("acts takes no id: %v", engine.Serves[len(engine.Serves)-1].Input)
+		}
 		if strings.Join(verbs, ",") != "hand-over,access-act,judge-directories,setuid-search,root-free,acts" ||
 			strings.Join(engine.Emits, ",") != "asked,done,refused" {
 			t.Errorf("node-engine serves %v and emits %v", verbs, engine.Emits)