diff --git a/lib/index.d.ts b/lib/index.d.ts
new file mode 100644
index 0000000..b2217e4
--- /dev/null
+++ b/lib/index.d.ts
@@ -0,0 +1,20 @@
+export type OptimisticWrapperFunction<
+  T = (...args: any[]) => any,
+> = T & {
+  // The .dirty(...) method of an optimistic function takes exactly the
+  // same parameter types as the original function.
+  dirty: T;
+};
+
+export type OptimisticWrapOptions = {
+  max?: number;
+  disposable?: boolean;
+  makeCacheKey?(...args: any[]): any;
+};
+
+export declare function defaultMakeCacheKey(...args: any[]): object;
+
+export declare function wrap<T>(
+  originalFunction: T,
+  options?: OptimisticWrapOptions,
+): OptimisticWrapperFunction<T>;
diff --git a/package.json b/package.json
index 490cfc4..cd6e99c 100644
--- a/package.json
+++ b/package.json
@@ -15,6 +15,7 @@
     "memoization"
   ],
   "main": "lib/index.js",
+  "types": "lib/index.d.ts",
   "license": "MIT",
   "homepage": "https://github.com/benjamn/optimism#readme",
   "repository": {