diff --git a/.gitignore b/.gitignore
index 53a29e3..4fe7736 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 coverage/
 node_modules/
 .DS_Store
-*.d.ts
+index.d.ts
+test.d.ts
 *.log
 yarn.lock
diff --git a/complex-types.d.ts b/complex-types.d.ts
new file mode 100644
index 0000000..5f3a4b9
--- /dev/null
+++ b/complex-types.d.ts
@@ -0,0 +1,35 @@
+import type {Parent} from 'unist'
+import type {PhrasingContent, BlockContent} from 'mdast'
+
+type DirectiveAttributes = Record<string, string>
+
+interface DirectiveFields {
+  name: string
+  attributes?: DirectiveAttributes
+}
+
+export interface TextDirective extends Parent, DirectiveFields {
+  type: 'textDirective'
+  children: PhrasingContent[]
+}
+
+export interface LeafDirective extends Parent, DirectiveFields {
+  type: 'leafDirective'
+  children: PhrasingContent[]
+}
+
+export interface ContainerDirective extends Parent, DirectiveFields {
+  type: 'containerDirective'
+  children: BlockContent[]
+}
+
+declare module 'mdast' {
+  interface StaticPhrasingContentMap {
+    textDirective: TextDirective
+  }
+
+  interface BlockContentMap {
+    containerDirective: ContainerDirective
+    leafDirective: LeafDirective
+  }
+}
diff --git a/index.js b/index.js
index 67787c6..1dfc5cd 100644
--- a/index.js
+++ b/index.js
@@ -1,18 +1,17 @@
 /**
+ * @typedef {import('mdast').BlockContent} BlockContent
+ * @typedef {import('mdast').Paragraph} Paragraph
  * @typedef {import('mdast-util-from-markdown').Handle} FromMarkdownHandle
  * @typedef {import('mdast-util-from-markdown').Extension} FromMarkdownExtension
- * @typedef {import('mdast-util-to-markdown/lib/types.js').Node} Node
- * @typedef {import('mdast-util-to-markdown/lib/types.js').Parent} Parent
+ * @typedef {import('mdast-util-from-markdown').CompileContext} CompileContext
+ * @typedef {import('mdast-util-from-markdown').Token} Token
  * @typedef {import('mdast-util-to-markdown/lib/types.js').Handle} ToMarkdownHandle
  * @typedef {import('mdast-util-to-markdown/lib/types.js').Context} Context
  * @typedef {import('mdast-util-to-markdown/lib/types.js').Options} ToMarkdownExtension
- *
- * @typedef {Record<string, string>} Attributes
- * @typedef {{name: string, attributes?: Attributes}} Directive
- *
- * @typedef {Parent & Directive & {type: 'textDirective', children: Array.<import('mdast').PhrasingContent>}} TextDirective
- * @typedef {Parent & Directive & {type: 'leafDirective', children: Array.<import('mdast').PhrasingContent>}} LeafDirective
- * @typedef {Parent & Directive & {type: 'containerDirective', children: Array.<import('mdast').BlockContent>}} ContainerDirective
+ * @typedef {import('./complex-types').ContainerDirective} ContainerDirective
+ * @typedef {import('./complex-types').LeafDirective} LeafDirective
+ * @typedef {import('./complex-types').TextDirective} TextDirective
+ * @typedef {ContainerDirective|LeafDirective|TextDirective} Directive
  */
 
 import {decodeEntity} from 'parse-entities/decode-entity.js'
@@ -112,21 +111,21 @@ function enterText(token) {
 }
 
 /**
- * @this {ThisParameterType<FromMarkdownHandle>}
- * @param {string} type
- * @param {Parameters<FromMarkdownHandle>[0]} token
+ * @this {CompileContext}
+ * @param {Directive['type']} type
+ * @param {Token} token
  */
 function enter(type, token) {
-  // @ts-expect-error: custom node.
   this.enter({type, name: '', attributes: {}, children: []}, token)
 }
 
 /**
- * @this {ThisParameterType<FromMarkdownHandle>}
- * @param {Parameters<FromMarkdownHandle>[0]} token
+ * @this {CompileContext}
+ * @param {Token} token
  */
 function exitName(token) {
-  this.stack[this.stack.length - 1].name = this.sliceSerialize(token)
+  const node = /** @type {Directive} */ (this.stack[this.stack.length - 1])
+  node.name = this.sliceSerialize(token)
 }
 
 /** @type {FromMarkdownHandle} */
@@ -150,33 +149,33 @@ function enterAttributes() {
 
 /** @type {FromMarkdownHandle} */
 function exitAttributeIdValue(token) {
-  /** @type {Array.<[string, string]>} */
-  // @ts-expect-error: custom.
-  const list = this.getData('directiveAttributes')
+  const list = /** @type {Array.<[string, string]>} */ (
+    this.getData('directiveAttributes')
+  )
   list.push(['id', decodeLight(this.sliceSerialize(token))])
 }
 
 /** @type {FromMarkdownHandle} */
 function exitAttributeClassValue(token) {
-  /** @type {Array.<[string, string]>} */
-  // @ts-expect-error: custom.
-  const list = this.getData('directiveAttributes')
+  const list = /** @type {Array.<[string, string]>} */ (
+    this.getData('directiveAttributes')
+  )
   list.push(['class', decodeLight(this.sliceSerialize(token))])
 }
 
 /** @type {FromMarkdownHandle} */
 function exitAttributeValue(token) {
-  /** @type {Array.<[string, string]>} */
-  // @ts-expect-error: custom.
-  const list = this.getData('directiveAttributes')
+  const list = /** @type {Array.<[string, string]>} */ (
+    this.getData('directiveAttributes')
+  )
   list[list.length - 1][1] = decodeLight(this.sliceSerialize(token))
 }
 
 /** @type {FromMarkdownHandle} */
 function exitAttributeName(token) {
-  /** @type {Array.<[string, string]>} */
-  // @ts-expect-error: custom.
-  const list = this.getData('directiveAttributes')
+  const list = /** @type {Array.<[string, string]>} */ (
+    this.getData('directiveAttributes')
+  )
 
   // Attribute names in CommonMark are significantly limited, so character
   // references can’t exist.
@@ -185,9 +184,9 @@ function exitAttributeName(token) {
 
 /** @type {FromMarkdownHandle} */
 function exitAttributes() {
-  /** @type {Array.<[string, string]>} */
-  // @ts-expect-error: custom.
-  const list = this.getData('directiveAttributes')
+  const list = /** @type {Array.<[string, string]>} */ (
+    this.getData('directiveAttributes')
+  )
   /** @type {Record.<string, string>} */
   const cleaned = {}
   let index = -1
@@ -204,7 +203,8 @@ function exitAttributes() {
 
   this.setData('directiveAttributes')
   this.resume() // Drop EOLs
-  this.stack[this.stack.length - 1].attributes = cleaned
+  const node = /** @type {Directive} */ (this.stack[this.stack.length - 1])
+  node.attributes = cleaned
 }
 
 /** @type {FromMarkdownHandle} */
@@ -214,7 +214,7 @@ function exit(token) {
 
 /**
  * @type {ToMarkdownHandle}
- * @param {TextDirective|LeafDirective|ContainerDirective} node
+ * @param {Directive} node
  */
 function handleDirective(node, _, context) {
   const prefix = fence(node)
@@ -241,18 +241,18 @@ function peekDirective() {
 }
 
 /**
- * @param {TextDirective|LeafDirective|ContainerDirective} node
+ * @param {Directive} node
  * @param {Context} context
  * @returns {string}
  */
 function label(node, context) {
-  /** @type {Parent} */
+  /** @type {Directive|Paragraph} */
   let label = node
 
   if (node.type === 'containerDirective') {
-    if (!inlineDirectiveLabel(node)) return ''
-    // @ts-expect-error: we just asserted it’s a parent.
-    label = node.children[0]
+    const head = (node.children || [])[0]
+    if (!inlineDirectiveLabel(head)) return ''
+    label = head
   }
 
   const exit = context.enter('label')
@@ -264,7 +264,7 @@ function label(node, context) {
 }
 
 /**
- * @param {TextDirective|LeafDirective|ContainerDirective} node
+ * @param {Directive} node
  * @param {Context} context
  * @returns {string}
  */
@@ -348,29 +348,27 @@ function attributes(node, context) {
 }
 
 /**
- * @param {TextDirective|LeafDirective|ContainerDirective} node
+ * @param {ContainerDirective} node
  * @param {Context} context
  * @returns {string}
  */
 function content(node, context) {
-  return containerFlow(
-    inlineDirectiveLabel(node)
-      ? Object.assign({}, node, {children: node.children.slice(1)})
-      : node,
-    context
-  )
+  const head = (node.children || [])[0]
+
+  if (inlineDirectiveLabel(head)) {
+    node = Object.assign({}, node, {children: node.children.slice(1)})
+  }
+
+  return containerFlow(node, context)
 }
 
 /**
- * @param {TextDirective|LeafDirective|ContainerDirective} node
- * @returns {boolean}
+ * @param {BlockContent} node
+ * @returns {node is Paragraph & {data: {directiveLabel: boolean}}}
  */
 function inlineDirectiveLabel(node) {
   return Boolean(
-    node.children &&
-      node.children[0] &&
-      node.children[0].data &&
-      node.children[0].data.directiveLabel
+    node && node.type === 'paragraph' && node.data && node.data.directiveLabel
   )
 }
 
@@ -395,7 +393,7 @@ function decodeIfPossible($0, $1) {
 }
 
 /**
- * @param {TextDirective|LeafDirective|ContainerDirective} node
+ * @param {Directive} node
  * @returns {string}
  */
 function fence(node) {
@@ -412,7 +410,7 @@ function fence(node) {
 
   return ':'.repeat(size)
 
-  /** @type {import('unist-util-visit-parents').Visitor<TextDirective|LeafDirective|ContainerDirective>} */
+  /** @type {import('unist-util-visit-parents').Visitor<Directive>} */
   function onvisit(_, parents) {
     let index = parents.length
     let nesting = 0
diff --git a/package.json b/package.json
index eec60b4..78343fc 100644
--- a/package.json
+++ b/package.json
@@ -31,6 +31,7 @@
   "main": "index.js",
   "types": "index.d.ts",
   "files": [
+    "complex-types.d.ts",
     "index.d.ts",
     "index.js"
   ],
@@ -57,7 +58,7 @@
     "xo": "^0.39.0"
   },
   "scripts": {
-    "build": "rimraf \"*.d.ts\" && tsc && type-coverage",
+    "build": "rimraf \"{index,test}.d.ts\" && tsc && type-coverage",
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
     "test-api": "node --conditions development test.js",
     "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node --conditions development test.js",
diff --git a/test.js b/test.js
index 2be02c9..44621bc 100644
--- a/test.js
+++ b/test.js
@@ -275,6 +275,7 @@ test('mdast -> markdown', (t) => {
         type: 'paragraph',
         children: [
           {type: 'text', value: 'a '},
+          // @ts-expect-error: `children`, `name` missing.
           {type: 'textDirective'},
           {type: 'text', value: ' b.'}
         ]
@@ -291,6 +292,7 @@ test('mdast -> markdown', (t) => {
         type: 'paragraph',
         children: [
           {type: 'text', value: 'a '},
+          // @ts-expect-error: `children` missing.
           {type: 'textDirective', name: 'b'},
           {type: 'text', value: ' c.'}
         ]
@@ -370,6 +372,7 @@ test('mdast -> markdown', (t) => {
           {
             type: 'textDirective',
             name: 'b',
+            // @ts-expect-error: should contain only `string`s
             attributes: {c: 'd', e: 'f', g: '', h: null, i: undefined, j: 2},
             children: []
           },
@@ -509,6 +512,7 @@ test('mdast -> markdown', (t) => {
   )
 
   t.deepEqual(
+    // @ts-expect-error: `children`, `name` missing.
     toMarkdown({type: 'leafDirective'}, {extensions: [directiveToMarkdown]}),
     '::\n',
     'should try to serialize a directive (leaf) w/o `name`'
@@ -516,6 +520,7 @@ test('mdast -> markdown', (t) => {
 
   t.deepEqual(
     toMarkdown(
+      // @ts-expect-error: `children` missing.
       {type: 'leafDirective', name: 'a'},
       {extensions: [directiveToMarkdown]}
     ),
@@ -567,7 +572,8 @@ test('mdast -> markdown', (t) => {
       {
         type: 'leafDirective',
         name: 'a',
-        attributes: {id: 'b', class: 'c d', key: 'e\nf'}
+        attributes: {id: 'b', class: 'c d', key: 'e\nf'},
+        children: []
       },
       {extensions: [directiveToMarkdown]}
     ),
@@ -577,6 +583,7 @@ test('mdast -> markdown', (t) => {
 
   t.deepEqual(
     toMarkdown(
+      // @ts-expect-error: `children`, `name` missing.
       {type: 'containerDirective'},
       {extensions: [directiveToMarkdown]}
     ),
@@ -586,6 +593,7 @@ test('mdast -> markdown', (t) => {
 
   t.deepEqual(
     toMarkdown(
+      // @ts-expect-error: `children` missing.
       {type: 'containerDirective', name: 'a'},
       {extensions: [directiveToMarkdown]}
     ),
@@ -611,7 +619,9 @@ test('mdast -> markdown', (t) => {
       {
         type: 'containerDirective',
         name: 'a',
-        children: [{type: 'heading', children: [{type: 'text', value: 'b'}]}]
+        children: [
+          {type: 'heading', depth: 1, children: [{type: 'text', value: 'b'}]}
+        ]
       },
       {extensions: [directiveToMarkdown]}
     ),
@@ -624,7 +634,9 @@ test('mdast -> markdown', (t) => {
       {
         type: 'containerDirective',
         name: 'a',
-        children: [{type: 'text', value: 'b\nc'}]
+        children: [
+          {type: 'paragraph', children: [{type: 'text', value: 'b\nc'}]}
+        ]
       },
       {extensions: [directiveToMarkdown]}
     ),
@@ -637,7 +649,8 @@ test('mdast -> markdown', (t) => {
       {
         type: 'containerDirective',
         name: 'a',
-        attributes: {id: 'b', class: 'c d', key: 'e\nf'}
+        attributes: {id: 'b', class: 'c d', key: 'e\nf'},
+        children: []
       },
       {extensions: [directiveToMarkdown]}
     ),
@@ -882,7 +895,7 @@ test('mdast -> markdown', (t) => {
       {
         type: 'paragraph',
         children: [
-          {type: 'textDirective', name: 'red'},
+          {type: 'textDirective', name: 'red', children: []},
           {type: 'text', value: ':'}
         ]
       },