diff --git a/lib/index.d.ts b/lib/index.d.ts
new file mode 100644
index 0000000..a9c587b
--- /dev/null
+++ b/lib/index.d.ts
@@ -0,0 +1,35 @@
+export type MethodName = string
+export type Method<Args, Returning> = (
+  ...Args
+) => Returning | Promise<Returning>
+
+export type Listener = (event: any) => void
+
+type BidirectionalMessagingOptions = {
+  addListener?: (eventName: string, handler: Listener) => void
+  removeListener?: (eventName: string, handler: Listener) => void
+  getMessageData?: (event: any) => any
+  postMessage(data: any, targetOrigin?: string): void | Promise<void>
+  targetOrigin?: string
+}
+
+export type CallerOptions = BidirectionalMessagingOptions
+export type ExposeOptions = BidirectionalMessagingOptions & {
+  isCallback?: boolean
+}
+
+export function caller<Returning extends any, Args extends any[]>(
+  methodName: MethodName,
+  options: CallerOptions
+): (...args: Args) => Promise<Returning>
+
+export function call<Returning extends any, Args extends any[]>(
+  methodName: MethodName,
+  ...args: Args
+): Promise<Returning>
+
+export function expose<Returning extends any, Args extends any[]>(
+  methodName: MethodName,
+  method: Method<Args, Returning>,
+  options: CallerOptions
+): (...args: Args) => Promise<Returning>