diff --git a/packages/docusaurus-mdx-loader/package.json b/packages/docusaurus-mdx-loader/package.json
index 0d1ee6bd2193..96d6e15ea9c8 100644
--- a/packages/docusaurus-mdx-loader/package.json
+++ b/packages/docusaurus-mdx-loader/package.json
@@ -6,6 +6,9 @@
   "publishConfig": {
     "access": "public"
   },
+  "scripts": {
+    "build": "tsc"
+  },
   "license": "MIT",
   "dependencies": {
     "@babel/parser": "^7.9.4",
@@ -27,6 +30,7 @@
     "url-loader": "^4.1.0"
   },
   "devDependencies": {
+    "@docusaurus/types": "^2.0.0-alpha.61",
     "remark": "^12.0.0",
     "remark-mdx": "^1.5.8",
     "to-vfile": "^6.0.0",
diff --git a/packages/docusaurus-mdx-loader/src/remark/rightToc/search.js b/packages/docusaurus-mdx-loader/src/remark/rightToc/search.js
index 5c89b314a269..516dc44d92d6 100644
--- a/packages/docusaurus-mdx-loader/src/remark/rightToc/search.js
+++ b/packages/docusaurus-mdx-loader/src/remark/rightToc/search.js
@@ -5,11 +5,29 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+// @ts-check
+
 const toString = require('mdast-util-to-string');
 const visit = require('unist-util-visit');
 const escapeHtml = require('escape-html');
 
+/** @typedef {import('@docusaurus/types').MarkdownRightTableOfContents} TOC */
+/** @typedef {import('unist').Node} Node */
+
+/**
+ * @typedef {Object} StringValuedNode
+ * @property {string} type
+ * @property {string} value
+ * @property {number} depth
+ * @property {Object} data
+ * @property {StringValuedNode[]} children
+ */
+
 // https://github.com/syntax-tree/mdast#heading
+/**
+ * @param {StringValuedNode | undefined} node
+ * @returns {string}
+ */
 function toValue(node) {
   if (node && node.type) {
     switch (node.type) {
@@ -34,11 +52,22 @@ function toValue(node) {
 
 // Visit all headings. We `slug` all headings (to account for
 // duplicates), but only take h2 and h3 headings.
+/**
+ * @param {StringValuedNode} node
+ * @returns {TOC[]}
+ */
 function search(node) {
+  /** @type {TOC[]} */
   const headings = [];
   let current = -1;
   let currentDepth = 0;
 
+  /**
+   * @param {StringValuedNode} child
+   * @param {number} index
+   * @param {Node | undefined} parent
+   * @returns {void}
+   */
   const onHeading = (child, index, parent) => {
     const value = toString(child);
 
diff --git a/packages/docusaurus-mdx-loader/tsconfig.json b/packages/docusaurus-mdx-loader/tsconfig.json
new file mode 100644
index 000000000000..460667f655b5
--- /dev/null
+++ b/packages/docusaurus-mdx-loader/tsconfig.json
@@ -0,0 +1,9 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "allowJs": true,
+    "noEmit": true,
+    "noImplicitAny": false
+  },
+  "include": ["src/"]
+}
diff --git a/packages/docusaurus-plugin-content-blog/index.d.ts b/packages/docusaurus-plugin-content-blog/index.d.ts
index 433c3d39bb4d..23174ea608c5 100644
--- a/packages/docusaurus-plugin-content-blog/index.d.ts
+++ b/packages/docusaurus-plugin-content-blog/index.d.ts
@@ -8,6 +8,8 @@
 /* eslint-disable camelcase */
 
 declare module '@theme/BlogPostPage' {
+  import type {MarkdownRightTableOfContents} from '@docusaurus/types';
+
   export type FrontMatter = {
     readonly title: string;
     readonly author?: string;
@@ -42,7 +44,7 @@ declare module '@theme/BlogPostPage' {
   export type Content = {
     readonly frontMatter: FrontMatter;
     readonly metadata: Metadata;
-    readonly rightToc: any; // TODO where to define this shared type?
+    readonly rightToc: MarkdownRightTableOfContents;
     (): JSX.Element;
   };
 
diff --git a/packages/docusaurus-theme-classic/package.json b/packages/docusaurus-theme-classic/package.json
index 60806b30e28a..e6fee495d9e7 100644
--- a/packages/docusaurus-theme-classic/package.json
+++ b/packages/docusaurus-theme-classic/package.json
@@ -28,6 +28,7 @@
     "react-router-dom": "^5.1.2",
     "react-toggle": "^4.1.1",
     "use-onclickoutside": "^0.3.1",
+    "@docusaurus/types": "^2.0.0-alpha.61",
     "@docusaurus/utils-validation": "^2.0.0-alpha.61"
   },
   "devDependencies": {
diff --git a/packages/docusaurus-theme-classic/src/theme/TOC/index.tsx b/packages/docusaurus-theme-classic/src/theme/TOC/index.tsx
index a6861e10d23e..ce1483d1fd42 100644
--- a/packages/docusaurus-theme-classic/src/theme/TOC/index.tsx
+++ b/packages/docusaurus-theme-classic/src/theme/TOC/index.tsx
@@ -8,14 +8,17 @@
 import React from 'react';
 
 import useTOCHighlight from '@theme/hooks/useTOCHighlight';
+import type {MarkdownRightTableOfContents} from '@docusaurus/types';
 import styles from './styles.module.css';
 
 const LINK_CLASS_NAME = 'table-of-contents__link';
 const ACTIVE_LINK_CLASS_NAME = 'table-of-contents__link--active';
 const TOP_OFFSET = 100;
 
+type TOCProps = {readonly headings: MarkdownRightTableOfContents[]};
+
 /* eslint-disable jsx-a11y/control-has-associated-label */
-function Headings({headings, isChild}: {headings; isChild?: boolean}) {
+function Headings({headings, isChild}: TOCProps & {isChild?: boolean}) {
   if (!headings.length) {
     return null;
   }
@@ -40,7 +43,7 @@ function Headings({headings, isChild}: {headings; isChild?: boolean}) {
   );
 }
 
-function TOC({headings}) {
+function TOC({headings}: TOCProps): JSX.Element {
   useTOCHighlight(LINK_CLASS_NAME, ACTIVE_LINK_CLASS_NAME, TOP_OFFSET);
   return (
     <div className={styles.tableOfContents}>
diff --git a/packages/docusaurus-types/src/index.d.ts b/packages/docusaurus-types/src/index.d.ts
index d2b0bf4c6192..7c93cbc25be0 100644
--- a/packages/docusaurus-types/src/index.d.ts
+++ b/packages/docusaurus-types/src/index.d.ts
@@ -270,3 +270,9 @@ export interface ValidationSchema<T> {
   unknown(): ValidationSchema<T>;
   append(data: any): ValidationSchema<T>;
 }
+
+export interface MarkdownRightTableOfContents {
+  readonly value: string;
+  readonly id: string;
+  readonly children: MarkdownRightTableOfContents[];
+}