diff --git a/dev/index.d.ts b/dev/index.d.ts
index 8efecf2..037dac3 100644
--- a/dev/index.d.ts
+++ b/dev/index.d.ts
@@ -1,7 +1,26 @@
 export {gfmStrikethroughHtml} from './lib/html.js'
-export {gfmStrikethrough, type Options} from './lib/syntax.js'
+export {gfmStrikethrough} from './lib/syntax.js'
 
+/**
+ * Configuration (optional).
+ */
+export interface Options {
+  /**
+   * Whether to support strikethrough with a single tilde (default: `true`).
+   *
+   * Single tildes work on github.com, but are technically prohibited by the
+   * GFM spec.
+   */
+  singleTilde?: boolean | null | undefined
+}
+
+/**
+ * Augment.
+ */
 declare module 'micromark-util-types' {
+  /**
+   * Token types.
+   */
   interface TokenTypeMap {
     strikethroughSequence: 'strikethroughSequence'
     strikethroughSequenceTemporary: 'strikethroughSequenceTemporary'
diff --git a/dev/lib/html.js b/dev/lib/html.js
index a75d1e3..bfbf44d 100644
--- a/dev/lib/html.js
+++ b/dev/lib/html.js
@@ -1,5 +1,5 @@
 /**
- * @typedef {import('micromark-util-types').HtmlExtension} HtmlExtension
+ * @import {HtmlExtension} from 'micromark-util-types'
  */
 
 /**
diff --git a/dev/lib/syntax.js b/dev/lib/syntax.js
index 9496b0b..dc4c187 100644
--- a/dev/lib/syntax.js
+++ b/dev/lib/syntax.js
@@ -1,19 +1,6 @@
 /**
- * @typedef {import('micromark-util-types').Event} Event
- * @typedef {import('micromark-util-types').Extension} Extension
- * @typedef {import('micromark-util-types').Resolver} Resolver
- * @typedef {import('micromark-util-types').State} State
- * @typedef {import('micromark-util-types').Token} Token
- * @typedef {import('micromark-util-types').TokenizeContext} TokenizeContext
- * @typedef {import('micromark-util-types').Tokenizer} Tokenizer
- *
- * @typedef Options
- *   Configuration (optional).
- * @property {boolean | null | undefined} [singleTilde=true]
- *   Whether to support strikethrough with a single tilde (default: `true`).
- *
- *   Single tildes work on github.com, but are technically prohibited by the
- *   GFM spec.
+ * @import {Options} from 'micromark-extension-gfm-strikethrough'
+ * @import {Event, Extension, Resolver, State, Token, TokenizeContext, Tokenizer} from 'micromark-util-types'
  */
 
 import {ok as assert} from 'devlop'
diff --git a/package.json b/package.json
index 947dee9..cb010db 100644
--- a/package.json
+++ b/package.json
@@ -100,7 +100,22 @@
       {
         "files": "**/*.ts",
         "rules": {
-          "@typescript-eslint/consistent-type-definitions": 0
+          "@typescript-eslint/array-type": [
+            "error",
+            {
+              "default": "generic"
+            }
+          ],
+          "@typescript-eslint/ban-types": [
+            "error",
+            {
+              "extendDefaults": true
+            }
+          ],
+          "@typescript-eslint/consistent-type-definitions": [
+            "error",
+            "interface"
+          ]
         }
       },
       {