diff --git a/lib.go b/lib.go
index f6e762f..c01444a 100644
--- a/lib.go
+++ b/lib.go
@@ -41,6 +41,17 @@ var acnQueue event.Queue
 var contactEventsQueue event.Queue
 var globalACN connectivity.ACN
 
+// ChatMessage API currently not officially documented, see
+// https://git.openprivacy.ca/cwtch.im/secure-development-handbook/issues/3
+// for latest updates for now
+//
+// A ChatMessage is the application-layer Cwtch message, delivered to the UI
+// as serialized json.
+type ChatMessage struct {
+	O int    `json:"o"`
+	D string `json:"d"`
+}
+
 //export c_StartCwtch
 func c_StartCwtch(dir_c *C.char, len C.int, tor_c *C.char, torLen C.int) {
 	dir := C.GoStringN(dir_c, len)
@@ -516,6 +527,40 @@ func SendMessage(profileOnion, handle, msg string) {
 	}
 }
 
+//export c_SendInvitation
+func c_SendInvitation(profile_ptr *C.char, profile_len C.int, handle_ptr *C.char, handle_len C.int, target_ptr *C.char, target_len C.int) {
+	profile := C.GoStringN(profile_ptr, profile_len)
+	handle := C.GoStringN(handle_ptr, handle_len)
+	target := C.GoStringN(target_ptr, target_len)
+	SendInvitation(profile, handle, target)
+}
+
+// Send an invitation from `profileOnion` to contact `handle` (peer or group)
+// asking them to add the contact `target`  (also peer or group).
+// For groups, the profile must already have `target` as a contact.
+func SendInvitation(profileOnion, handle, target string) {
+	profile := application.GetPeer(profileOnion)
+	ph := utils.NewPeerHelper(profile)
+
+	var invite ChatMessage
+	if ph.IsGroup(target) {
+		bundle, _ := profile.GetContact(profile.GetGroup(target).GroupServer).GetAttribute(string(model.BundleType))
+		inviteStr, err := profile.GetGroup(target).Invite()
+		if err == nil {
+			invite = ChatMessage{O: 101, D: fmt.Sprintf("tofubundle:server:%s||%s", base64.StdEncoding.EncodeToString([]byte(bundle)), inviteStr)}
+		}
+	} else {
+		invite = ChatMessage{O: 100, D: target}
+	}
+
+	inviteBytes, err := json.Marshal(invite)
+	if err != nil {
+		log.Errorf("malformed invite: %v", err)
+	} else {
+		SendMessage(profileOnion, handle, string(inviteBytes))
+	}
+}
+
 //export c_ResetTor
 func c_ResetTor() {
 	ResetTor()