diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..27005a8
--- /dev/null
+++ b/index.d.ts
@@ -0,0 +1,13 @@
+/**
+ * Determines the type of the given collection, or returns false.
+ *
+ * @param {unknown} value The potential collection
+ * @returns {'Map' | 'Set' | 'WeakMap' | 'WeakSet' | false} 'Map' | 'Set' | 'WeakMap' | 'WeakSet' | false
+ */
+declare function whichCollection<K, V>(value: Map<K, V>): 'Map';
+declare function whichCollection<T>(value: Set<T>): 'Set';
+declare function whichCollection<K extends WeakKey, V>(value: WeakMap<K, V>): 'WeakMap';
+declare function whichCollection<T extends WeakKey>(value: WeakSet<T>): 'WeakSet';
+declare function whichCollection(value: null | undefined | boolean | number | bigint | symbol | unknown): false;
+
+export = whichCollection;
diff --git a/index.js b/index.js
index 71c7f95..cc8d097 100644
--- a/index.js
+++ b/index.js
@@ -5,7 +5,8 @@ var isSet = require('is-set');
 var isWeakMap = require('is-weakmap');
 var isWeakSet = require('is-weakset');
 
-module.exports = function whichCollection(value) {
+/** @type {import('.')} */
+module.exports = function whichCollection(/** @type {unknown} */ value) {
 	if (value && typeof value === 'object') {
 		if (isMap(value)) {
 			return 'Map';
diff --git a/package.json b/package.json
index 39c1b6f..e8e213c 100644
--- a/package.json
+++ b/package.json
@@ -14,6 +14,7 @@
 		"prepublish": "not-in-publish || npm run prepublishOnly",
 		"lint": "eslint --ext=js,mjs .",
 		"pretest": "npm run lint",
+		"postlint": "tsc -p . && attw -P",
 		"tests-only": "nyc tape 'test/**/*.js'",
 		"test": "npm run tests-only",
 		"posttest": "npx aud --production",
@@ -42,7 +43,11 @@
 	},
 	"homepage": "https://github.com/inspect-js/which-collection#readme",
 	"devDependencies": {
+		"@arethetypeswrong/cli": "^0.15.0",
 		"@ljharb/eslint-config": "^21.1.0",
+		"@types/for-each": "^0.3.3",
+		"@types/object-inspect": "^1.8.4",
+		"@types/tape": "^5.6.4",
 		"aud": "^2.0.4",
 		"auto-changelog": "^2.4.0",
 		"eslint": "=8.8.0",
@@ -52,7 +57,8 @@
 		"nyc": "^10.3.2",
 		"object-inspect": "^1.13.1",
 		"safe-publish-latest": "^2.0.0",
-		"tape": "^5.7.5"
+		"tape": "^5.7.5",
+		"typescript": "next"
 	},
 	"dependencies": {
 		"is-map": "^2.0.3",
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..2002ce5
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,49 @@
+{
+  "compilerOptions": {
+    /* Visit https://aka.ms/tsconfig to read more about this file */
+
+    /* Projects */
+
+    /* Language and Environment */
+    "target": "ESNext",                                  /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */
+    // "lib": [],                                        /* Specify a set of bundled library declaration files that describe the target runtime environment. */
+    // "noLib": true,                                    /* Disable including any library files, including the default lib.d.ts. */
+    "useDefineForClassFields": true,                     /* Emit ECMAScript-standard-compliant class fields. */
+    // "moduleDetection": "auto",                        /* Control what method is used to detect module-format JS files. */
+
+    /* Modules */
+    "module": "commonjs",                                /* Specify what module code is generated. */
+    // "rootDir": "./",                                  /* Specify the root folder within your source files. */
+    // "moduleResolution": "node10",                     /* Specify how TypeScript looks up a file from a given module specifier. */
+    // "baseUrl": "./",                                  /* Specify the base directory to resolve non-relative module names. */
+    // "paths": {},                                      /* Specify a set of entries that re-map imports to additional lookup locations. */
+    // "rootDirs": [],                                   /* Allow multiple folders to be treated as one when resolving modules. */
+    "typeRoots": ["types"],                              /* Specify multiple folders that act like './node_modules/@types'. */
+    "resolveJsonModule": true,                           /* Enable importing .json files. */
+    // "allowArbitraryExtensions": true,                 /* Enable importing files with any extension, provided a declaration file is present. */
+
+    /* JavaScript Support */
+    "allowJs": true,                                     /* Allow JavaScript files to be a part of your program. Use the 'checkJS' option to get errors from these files. */
+    "checkJs": true,                                     /* Enable error reporting in type-checked JavaScript files. */
+    "maxNodeModuleJsDepth": 0,                           /* Specify the maximum folder depth used for checking JavaScript files from 'node_modules'. Only applicable with 'allowJs'. */
+
+    /* Emit */
+    "declaration": true,                                 /* Generate .d.ts files from TypeScript and JavaScript files in your project. */
+    "declarationMap": true,                              /* Create sourcemaps for d.ts files. */
+    "noEmit": true,                                      /* Disable emitting files from a compilation. */
+
+    /* Interop Constraints */
+    "allowSyntheticDefaultImports": true,                /* Allow 'import x from y' when a module doesn't have a default export. */
+    "esModuleInterop": true,                             /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */
+    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */
+
+    /* Type Checking */
+    "strict": true,                                      /* Enable all strict type-checking options. */
+
+    /* Completeness */
+    //"skipLibCheck": true                                 /* Skip type checking all .d.ts files. */
+  },
+  "exclude": [
+    "coverage"
+  ]
+}