diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 67fede4..6fd02cd 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -16,7 +16,7 @@ jobs:
         node-version: 20.x
 
     - name: Install tools
-      run: npm install --location=global bslint
+      run: npm install --location=global bslint typescript
 
     - name: Install dependencies
       run: npm install
@@ -24,6 +24,9 @@ jobs:
     - name: Lint
       run: npm run lint
 
+    - name: Lint types
+      run: npm run lint-types
+
   test:
     name: Test
     runs-on: ${{ matrix.os }}
diff --git a/lib/fs.js b/lib/fs.js
index b682525..a63d9aa 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -6,6 +6,7 @@ function promisify(func) {
   return function(...args) {
     return new Promise((resolve, reject) => {
       args.push(wrap(resolve, reject));
+      // @ts-ignore
       func.call(this, ...args);
     });
   };
@@ -33,3 +34,4 @@ exports.rename = promisify(fs.rename);
 exports.readdir = promisify(fs.readdir);
 exports.stat = promisify(fs.stat);
 exports.unlink = promisify(fs.unlink);
+exports.unsupported = false;
diff --git a/lib/logger.js b/lib/logger.js
index 3d37a4c..86e8909 100644
--- a/lib/logger.js
+++ b/lib/logger.js
@@ -11,6 +11,16 @@ const assert = require('bsert');
 const format = require('./format');
 const fs = require('./fs');
 
+/**
+ * @typedef {Object} LoggerOptions
+ * @property {String} [level=none]
+ * @property {Boolean} [colors]
+ * @property {Boolean} [console]
+ * @property {String} [filename]
+ * @property {Number} [maxFileSize]
+ * @property {Number} [maxFiles]
+ */
+
 /**
  * Logger
  */
@@ -19,9 +29,7 @@ class Logger {
   /**
    * Create a logger.
    * @constructor
-   * @param {(String|Object)?} options/level
-   * @param {String?} options.level
-   * @param {Boolean} [options.colors=true]
+   * @param {(String|LoggerOptions)} [options]
    */
 
   constructor(options) {
@@ -317,18 +325,17 @@ class Logger {
 
   /**
    * Set or reset the log level.
-   * @param {String} level
+   * @param {String} levelName
    */
 
-  setLevel(name) {
-    const level = Logger.levels[name.toUpperCase()];
+  setLevel(levelName) {
+    const level = Logger.levels[levelName.toUpperCase()];
     assert(level != null, 'Invalid log level.');
     this.level = level;
   }
 
   /**
    * Output a log to the `error` log level.
-   * @param {String|Object|Error} err
    * @param {...Object} args
    */
 
@@ -348,7 +355,6 @@ class Logger {
 
   /**
    * Output a log to the `warning` log level.
-   * @param {String|Object} obj
    * @param {...Object} args
    */
 
@@ -368,7 +374,6 @@ class Logger {
 
   /**
    * Output a log to the `info` log level.
-   * @param {String|Object} obj
    * @param {...Object} args
    */
 
@@ -388,7 +393,6 @@ class Logger {
 
   /**
    * Output a log to the `debug` log level.
-   * @param {String|Object} obj
    * @param {...Object} args
    */
 
@@ -408,7 +412,6 @@ class Logger {
 
   /**
    * Output a log to the `spam` log level.
-   * @param {String|Object} obj
    * @param {...Object} args
    */
 
@@ -429,7 +432,7 @@ class Logger {
   /**
    * Output a log to the desired log level.
    * Note that this bypasses the level check.
-   * @param {String} level
+   * @param {Number} level
    * @param {String|null} module
    * @param {Object[]} args
    */
@@ -464,7 +467,7 @@ class Logger {
 
   /**
    * Write log to the console.
-   * @param {String} level
+   * @param {Number} level
    * @param {String|null} module
    * @param {Object[]} args
    */
@@ -525,7 +528,7 @@ class Logger {
 
   /**
    * Write a string to the output stream (usually a file).
-   * @param {String} level
+   * @param {Number} level
    * @param {String|null} module
    * @param {Object[]} args
    */
@@ -564,7 +567,6 @@ class Logger {
   /**
    * Helper to parse an error into a nicer
    * format. Call's `log` internally.
-   * @private
    * @param {Number} level
    * @param {String|null} module
    * @param {Error} err
@@ -689,7 +691,7 @@ class LoggerContext {
 
   /**
    * Set or reset the log level.
-   * @param {String} level
+   * @param {String} name
    */
 
   setLevel(name) {
@@ -698,7 +700,6 @@ class LoggerContext {
 
   /**
    * Output a log to the `error` log level.
-   * @param {String|Object|Error} err
    * @param {...Object} args
    */
 
@@ -718,7 +719,6 @@ class LoggerContext {
 
   /**
    * Output a log to the `warning` log level.
-   * @param {String|Object} obj
    * @param {...Object} args
    */
 
@@ -738,7 +738,6 @@ class LoggerContext {
 
   /**
    * Output a log to the `info` log level.
-   * @param {String|Object} obj
    * @param {...Object} args
    */
 
@@ -758,7 +757,6 @@ class LoggerContext {
 
   /**
    * Output a log to the `debug` log level.
-   * @param {String|Object} obj
    * @param {...Object} args
    */
 
@@ -778,7 +776,6 @@ class LoggerContext {
 
   /**
    * Output a log to the `spam` log level.
-   * @param {String|Object} obj
    * @param {...Object} args
    */
 
@@ -799,7 +796,7 @@ class LoggerContext {
   /**
    * Output a log to the desired log level.
    * Note that this bypasses the level check.
-   * @param {String} level
+   * @param {Number} level
    * @param {Object[]} args
    */
 
diff --git a/package-lock.json b/package-lock.json
index 2329e00..209f64f 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12,7 +12,8 @@
         "bsert": "~0.0.12"
       },
       "devDependencies": {
-        "bmocha": "^2.1.8"
+        "bmocha": "^2.1.8",
+        "bts-type-deps": "^0.0.3"
       },
       "engines": {
         "node": ">=8.0.0"
@@ -38,6 +39,12 @@
       "engines": {
         "node": ">=8.0.0"
       }
+    },
+    "node_modules/bts-type-deps": {
+      "version": "0.0.3",
+      "resolved": "https://registry.npmjs.org/bts-type-deps/-/bts-type-deps-0.0.3.tgz",
+      "integrity": "sha512-OQHGWhX5amae6Vj6ShlGaQu0sNCICgJ5YspNZPRzfR5RobrD+wjm5vkZK/J3EH5b/ymxqSWo9VkiFNpCxjaG2Q==",
+      "dev": true
     }
   }
 }
diff --git a/package.json b/package.json
index 04ce61e..e953e4e 100644
--- a/package.json
+++ b/package.json
@@ -17,13 +17,15 @@
   "main": "./lib/blgr.js",
   "scripts": {
     "lint": "eslint lib/",
+    "lint-types": "tsc -p .",
     "test": "bmocha --reporter spec test/*-test.js"
   },
   "dependencies": {
     "bsert": "~0.0.12"
   },
   "devDependencies": {
-    "bmocha": "^2.1.8"
+    "bmocha": "^2.1.8",
+    "bts-type-deps": "^0.0.3"
   },
   "engines": {
     "node": ">=8.0.0"
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..da7a94b
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,31 @@
+{
+  "include": [
+    "lib/**/*.js"
+  ],
+  "compilerOptions": {
+    "rootDir": ".",
+    "target": "ES2020",
+    "lib": [
+      "ES2020"
+    ],
+
+    "noEmit": true,
+
+    "allowJs": true,
+    "checkJs": true,
+    "maxNodeModuleJsDepth": 10,
+
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "resolveJsonModule": true,
+
+    "stripInternal": true,
+    "noImplicitThis": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": false,
+
+    "typeRoots": [
+      "node_modules/bts-type-deps/types"
+    ]
+  }
+}