diff --git a/keyserver/addons/rust-node-addon/index.js b/keyserver/addons/rust-node-addon/index.js
index 5db55e7c8..0827bcf82 100644
--- a/keyserver/addons/rust-node-addon/index.js
+++ b/keyserver/addons/rust-node-addon/index.js
@@ -1,49 +1,39 @@
 // @flow
 
 import invariant from 'invariant';
 import { createRequire } from 'module';
 
+import type { RustNativeBindingAPI } from 'lib/types/rust-binding-types.js';
+
 const { platform, arch } = process;
 
 const importMetaURL = import.meta.url;
 invariant(importMetaURL, 'import.meta.url should be set');
 const require = createRequire(importMetaURL);
 
-type RustAPI = {
-  +registerUser: (
-    userId: string,
-    deviceId: string,
-    username: string,
-    password: string,
-    userPublicKey: string,
-  ) => Promise<string>,
-  +deleteUser: (userId: string) => Promise<boolean>,
-};
-
-async function getRustAPI(): Promise<RustAPI> {
+async function getRustAPI(): Promise<RustNativeBindingAPI> {
   let nativeBinding = null;
   if (platform === 'darwin' && arch === 'x64') {
     // $FlowFixMe
     nativeBinding = require('./napi/rust-node-addon.darwin-x64.node');
   } else if (platform === 'darwin' && arch === 'arm64') {
     // $FlowFixMe
     nativeBinding = require('./napi/rust-node-addon.darwin-arm64.node');
   } else if (platform === 'linux' && arch === 'x64') {
     // $FlowFixMe
     nativeBinding = require('./napi/rust-node-addon.linux-x64-gnu.node');
   } else if (platform === 'linux' && arch === 'arm64') {
     // $FlowFixMe
     nativeBinding = require('./napi/rust-node-addon.linux-arm64-gnu.node');
   } else {
     throw new Error(`Unsupported OS: ${platform}, architecture: ${arch}`);
   }
 
   if (!nativeBinding) {
-    throw new Error('Failed to load native binding');
+    throw new Error('Failed to load Rust native binding');
   }
 
-  const { registerUser, deleteUser } = nativeBinding;
-  return { registerUser, deleteUser };
+  return nativeBinding;
 }
 
 export { getRustAPI };
diff --git a/lib/types/rust-binding-types.js b/lib/types/rust-binding-types.js
new file mode 100644
index 000000000..debb832ee
--- /dev/null
+++ b/lib/types/rust-binding-types.js
@@ -0,0 +1,28 @@
+// @flow
+
+type tunnelbrokerOnReceiveCallback = (
+  err: Error | null,
+  payload: string,
+) => mixed;
+
+declare class TunnelbrokerClientClass {
+  constructor(
+    deviceId: string,
+    onReceiveCallback: tunnelbrokerOnReceiveCallback,
+  ): TunnelbrokerClientClass;
+  publish(toDeviceId: string, payload: string): Promise<void>;
+}
+
+type RustNativeBindingAPI = {
+  +registerUser: (
+    userId: string,
+    deviceId: string,
+    username: string,
+    password: string,
+    userPublicKey: string,
+  ) => Promise<string>,
+  +deleteUser: (userId: string) => Promise<boolean>,
+  +TunnelbrokerClient: Class<TunnelbrokerClientClass>,
+};
+
+export type { RustNativeBindingAPI };