diff --git a/packages/docusaurus-plugin-content-docs/src/client/docsClientUtils.ts b/packages/docusaurus-plugin-content-docs/src/client/docsClientUtils.ts
index a6e3359fc52f..752a53d91edc 100644
--- a/packages/docusaurus-plugin-content-docs/src/client/docsClientUtils.ts
+++ b/packages/docusaurus-plugin-content-docs/src/client/docsClientUtils.ts
@@ -59,12 +59,10 @@ export function getActivePlugin(
 export const getLatestVersion = (data: GlobalPluginData): GlobalVersion =>
   data.versions.find((version) => version.isLast)!;
 
-// Note: return undefined on doc-unrelated pages,
-// because there's no version currently considered as active
-export const getActiveVersion = (
+export function getActiveVersion(
   data: GlobalPluginData,
   pathname: string,
-): GlobalVersion | undefined => {
+): GlobalVersion | undefined {
   const lastVersion = getLatestVersion(data);
   // Last version is a route like /docs/*,
   // we need to match it last or it would match /docs/version-1.0/* as well
@@ -80,12 +78,12 @@ export const getActiveVersion = (
         strict: false,
       }),
   );
-};
+}
 
-export const getActiveDocContext = (
+export function getActiveDocContext(
   data: GlobalPluginData,
   pathname: string,
-): ActiveDocContext => {
+): ActiveDocContext {
   const activeVersion = getActiveVersion(data, pathname);
   const activeDoc = activeVersion?.docs.find(
     (doc) =>
@@ -119,15 +117,15 @@ export const getActiveDocContext = (
     activeDoc,
     alternateDocVersions: alternateVersionDocs,
   };
-};
+}
 
-export const getDocVersionSuggestions = (
+export function getDocVersionSuggestions(
   data: GlobalPluginData,
   pathname: string,
-): DocVersionSuggestions => {
+): DocVersionSuggestions {
   const latestVersion = getLatestVersion(data);
   const activeDocContext = getActiveDocContext(data, pathname);
   const latestDocSuggestion: GlobalDoc | undefined =
     activeDocContext?.alternateDocVersions[latestVersion.name];
   return {latestDocSuggestion, latestVersionSuggestion: latestVersion};
-};
+}
diff --git a/packages/docusaurus-plugin-content-docs/src/client/index.ts b/packages/docusaurus-plugin-content-docs/src/client/index.ts
index 4923a069d0a6..69fedc1450d3 100644
--- a/packages/docusaurus-plugin-content-docs/src/client/index.ts
+++ b/packages/docusaurus-plugin-content-docs/src/client/index.ts
@@ -43,67 +43,61 @@ export const useDocsData = (pluginId: string | undefined): GlobalPluginData =>
   }) as GlobalPluginData;
 
 // TODO this feature should be provided by docusaurus core
-export const useActivePlugin = (
+export function useActivePlugin(
   options: UseDataOptions = {},
-): ActivePlugin | undefined => {
+): ActivePlugin | undefined {
   const data = useAllDocsData();
   const {pathname} = useLocation();
   return getActivePlugin(data, pathname, options);
-};
+}
 
-export const useActivePluginAndVersion = (
+export function useActivePluginAndVersion(
   options: UseDataOptions = {},
 ):
-  | undefined
-  | {activePlugin: ActivePlugin; activeVersion: GlobalVersion | undefined} => {
+  | {activePlugin: ActivePlugin; activeVersion: GlobalVersion | undefined}
+  | undefined {
   const activePlugin = useActivePlugin(options);
   const {pathname} = useLocation();
-  if (activePlugin) {
-    const activeVersion = getActiveVersion(activePlugin.pluginData, pathname);
-    return {
-      activePlugin,
-      activeVersion,
-    };
+  if (!activePlugin) {
+    return undefined;
   }
-  return undefined;
-};
+  const activeVersion = getActiveVersion(activePlugin.pluginData, pathname);
+  return {
+    activePlugin,
+    activeVersion,
+  };
+}
 
-// versions are returned ordered (most recent first)
-export const useVersions = (pluginId: string | undefined): GlobalVersion[] => {
+export function useVersions(pluginId: string | undefined): GlobalVersion[] {
   const data = useDocsData(pluginId);
   return data.versions;
-};
+}
 
-export const useLatestVersion = (
-  pluginId: string | undefined,
-): GlobalVersion => {
+export function useLatestVersion(pluginId: string | undefined): GlobalVersion {
   const data = useDocsData(pluginId);
   return getLatestVersion(data);
-};
+}
 
-// Note: return undefined on doc-unrelated pages,
-// because there's no version currently considered as active
-export const useActiveVersion = (
+export function useActiveVersion(
   pluginId: string | undefined,
-): GlobalVersion | undefined => {
+): GlobalVersion | undefined {
   const data = useDocsData(pluginId);
   const {pathname} = useLocation();
   return getActiveVersion(data, pathname);
-};
+}
 
-export const useActiveDocContext = (
+export function useActiveDocContext(
   pluginId: string | undefined,
-): ActiveDocContext => {
+): ActiveDocContext {
   const data = useDocsData(pluginId);
   const {pathname} = useLocation();
   return getActiveDocContext(data, pathname);
-};
+}
 
-// Useful to say "hey, you are not on the latest docs version, please switch"
-export const useDocVersionSuggestions = (
+export function useDocVersionSuggestions(
   pluginId: string | undefined,
-): DocVersionSuggestions => {
+): DocVersionSuggestions {
   const data = useDocsData(pluginId);
   const {pathname} = useLocation();
   return getDocVersionSuggestions(data, pathname);
-};
+}
diff --git a/packages/docusaurus-plugin-content-docs/src/plugin-content-docs.d.ts b/packages/docusaurus-plugin-content-docs/src/plugin-content-docs.d.ts
index a8ae90e6afb1..bf5008ed985f 100644
--- a/packages/docusaurus-plugin-content-docs/src/plugin-content-docs.d.ts
+++ b/packages/docusaurus-plugin-content-docs/src/plugin-content-docs.d.ts
@@ -554,56 +554,18 @@ declare module '@theme/DocBreadcrumbs' {
 
 declare module '@theme/DocPage' {
   import type {PropVersionMetadata} from '@docusaurus/plugin-content-docs';
-  import type {DocumentRoute} from '@theme/DocItem';
+  import type {RouteConfigComponentProps} from 'react-router-config';
+  import type {Required} from 'utility-types';
 
-  export interface Props {
-    readonly location: {readonly pathname: string};
+  export interface Props extends Required<RouteConfigComponentProps, 'route'> {
     readonly versionMetadata: PropVersionMetadata;
-    readonly route: {
-      readonly path: string;
-      readonly component: () => JSX.Element;
-      readonly routes: DocumentRoute[];
-    };
   }
 
   export default function DocPage(props: Props): JSX.Element;
 }
 
-declare module '@theme/DocPage/Layout' {
-  import type {ReactNode} from 'react';
-
-  export interface Props {
-    children: ReactNode;
-  }
-
-  export default function DocPageLayout(props: Props): JSX.Element;
-}
-
-declare module '@theme/DocPage/Layout/Aside' {
-  import type {Dispatch, SetStateAction} from 'react';
-  import type {PropSidebar} from '@docusaurus/plugin-content-docs';
-
-  export interface Props {
-    sidebar: PropSidebar;
-    hiddenSidebarContainer: boolean;
-    setHiddenSidebarContainer: Dispatch<SetStateAction<boolean>>;
-  }
-
-  export default function DocPageLayoutAside(props: Props): JSX.Element;
-}
-
-declare module '@theme/DocPage/Layout/Main' {
-  import type {ReactNode} from 'react';
-
-  export interface Props {
-    hiddenSidebarContainer: boolean;
-    children: ReactNode;
-  }
-
-  export default function DocPageLayoutMain(props: Props): JSX.Element;
-}
-
-// TODO until TS supports exports field... hope it's in 4.6
+// TODO TS only supports reading `exports` in 4.7. We will need to merge the
+// type defs (and JSDoc) here with the implementation after that
 declare module '@docusaurus/plugin-content-docs/client' {
   import type {UseDataOptions} from '@docusaurus/types';
 
@@ -617,6 +579,11 @@ declare module '@docusaurus/plugin-content-docs/client' {
     alternateDocVersions: {[versionName: string]: GlobalDoc};
   };
   export type GlobalDoc = {
+    /**
+     * For generated index pages, this is the `slug`, **not** `permalink`
+     * (without base URL). Because slugs have leading slashes but IDs don't,
+     * there won't be clashes.
+     */
     id: string;
     path: string;
     sidebar: string | undefined;
@@ -627,7 +594,8 @@ declare module '@docusaurus/plugin-content-docs/client' {
     label: string;
     isLast: boolean;
     path: string;
-    mainDocId: string; // home doc (if docs homepage configured), or first doc
+    /** The doc with `slug: /`, or first doc in first sidebar */
+    mainDocId: string;
     docs: GlobalDoc[];
     sidebars?: {[sidebarId: string]: GlobalSidebar};
   };
@@ -645,9 +613,9 @@ declare module '@docusaurus/plugin-content-docs/client' {
     breadcrumbs: boolean;
   };
   export type DocVersionSuggestions = {
-    // suggest the latest version
+    /** suggest the latest version */
     latestVersionSuggestion: GlobalVersion;
-    // suggest the same doc, in latest version (if exist)
+    /** suggest the same doc, in latest version (if exist) */
     latestDocSuggestion?: GlobalDoc;
   };
 
@@ -661,12 +629,20 @@ declare module '@docusaurus/plugin-content-docs/client' {
   ) =>
     | {activePlugin: ActivePlugin; activeVersion: GlobalVersion | undefined}
     | undefined;
+  /** Versions are returned ordered (most recent first). */
   export const useVersions: (pluginId?: string) => GlobalVersion[];
   export const useLatestVersion: (pluginId?: string) => GlobalVersion;
+  /**
+   * Returns `undefined` on doc-unrelated pages, because there's no version
+   * currently considered as active.
+   */
   export const useActiveVersion: (
     pluginId?: string,
   ) => GlobalVersion | undefined;
   export const useActiveDocContext: (pluginId?: string) => ActiveDocContext;
+  /**
+   * Useful to say "hey, you are not on the latest docs version, please switch"
+   */
   export const useDocVersionSuggestions: (
     pluginId?: string,
   ) => DocVersionSuggestions;
diff --git a/packages/docusaurus-preset-classic/src/preset-classic.d.ts b/packages/docusaurus-preset-classic/src/preset-classic.d.ts
index 57fbfdbb5da8..1e65f826fa31 100644
--- a/packages/docusaurus-preset-classic/src/preset-classic.d.ts
+++ b/packages/docusaurus-preset-classic/src/preset-classic.d.ts
@@ -17,13 +17,30 @@ import type {UserThemeConfig as ClassicThemeConfig} from '@docusaurus/theme-comm
 import type {UserThemeConfig as AlgoliaThemeConfig} from '@docusaurus/theme-search-algolia';
 
 export type Options = {
+  /**
+   * Options for `@docusaurus/plugin-debug`. Use `false` to disable, or `true`
+   * to enable even in production.
+   */
   debug?: boolean;
+  /** Options for `@docusaurus/plugin-content-docs`. Use `false` to disable. */
   docs?: false | DocsPluginOptions;
+  /** Options for `@docusaurus/plugin-content-blog`. Use `false` to disable. */
   blog?: false | BlogPluginOptions;
+  /** Options for `@docusaurus/plugin-content-pages`. Use `false` to disable. */
   pages?: false | PagesPluginOptions;
+  /** Options for `@docusaurus/plugin-sitemap`. Use `false` to disable. */
   sitemap?: false | SitemapPluginOptions;
+  /** Options for `@docusaurus/theme-classic`. */
   theme?: ThemeOptions;
+  /**
+   * Options for `@docusaurus/plugin-google-analytics`. Only enabled when the
+   * key is present.
+   */
   googleAnalytics?: GAPluginOptions;
+  /**
+   * Options for `@docusaurus/plugin-google-gtag`. Only enabled when the key
+   * is present.
+   */
   gtag?: GtagPluginOptions;
 };
 
diff --git a/packages/docusaurus-theme-classic/src/theme-classic.d.ts b/packages/docusaurus-theme-classic/src/theme-classic.d.ts
index b8a29d637dc1..18da1b9d35d1 100644
--- a/packages/docusaurus-theme-classic/src/theme-classic.d.ts
+++ b/packages/docusaurus-theme-classic/src/theme-classic.d.ts
@@ -12,6 +12,14 @@
 /// <reference types="@docusaurus/plugin-content-blog" />
 /// <reference types="@docusaurus/plugin-content-pages" />
 
+// This file, like all the other ambient declaration files for plugins, is
+// needed for TS to understand our `@theme` alias. The export signatures are
+// duplicated from the implementation, which is fine, since every module only
+// default-exports a React component.
+// TODO we'll eventually migrate to TS `paths` option. This is not easy due to
+// our theme shadowing—we probably need the user to specify multiple theme paths
+// in their tsconfig.
+
 declare module '@docusaurus/theme-classic' {
   export type Options = {
     customCss?: string | string[];
@@ -188,6 +196,40 @@ declare module '@theme/DocItemFooter' {
   export default function DocItemFooter(props: Props): JSX.Element;
 }
 
+declare module '@theme/DocPage/Layout' {
+  import type {ReactNode} from 'react';
+
+  export interface Props {
+    readonly children: ReactNode;
+  }
+
+  export default function DocPageLayout(props: Props): JSX.Element;
+}
+
+declare module '@theme/DocPage/Layout/Aside' {
+  import type {Dispatch, SetStateAction} from 'react';
+  import type {PropSidebar} from '@docusaurus/plugin-content-docs';
+
+  export interface Props {
+    readonly sidebar: PropSidebar;
+    readonly hiddenSidebarContainer: boolean;
+    readonly setHiddenSidebarContainer: Dispatch<SetStateAction<boolean>>;
+  }
+
+  export default function DocPageLayoutAside(props: Props): JSX.Element;
+}
+
+declare module '@theme/DocPage/Layout/Main' {
+  import type {ReactNode} from 'react';
+
+  export interface Props {
+    readonly hiddenSidebarContainer: boolean;
+    readonly children: ReactNode;
+  }
+
+  export default function DocPageLayoutMain(props: Props): JSX.Element;
+}
+
 declare module '@theme/DocPaginator' {
   import type {PropNavigation} from '@docusaurus/plugin-content-docs';
 
@@ -242,7 +284,7 @@ declare module '@theme/DocSidebar/Desktop/Content' {
 
 declare module '@theme/DocSidebar/Desktop/CollapseButton' {
   export interface Props {
-    onClick: React.MouseEventHandler;
+    readonly onClick: React.MouseEventHandler;
   }
 
   export default function CollapseButton(props: Props): JSX.Element;
@@ -269,7 +311,7 @@ declare module '@theme/DocSidebarItem/Link' {
   import type {PropSidebarItemLink} from '@docusaurus/plugin-content-docs';
 
   export interface Props extends DocSidebarItemProps {
-    item: PropSidebarItemLink;
+    readonly item: PropSidebarItemLink;
   }
 
   export default function DocSidebarItemLink(props: Props): JSX.Element;
@@ -280,7 +322,7 @@ declare module '@theme/DocSidebarItem/Html' {
   import type {PropSidebarItemHtml} from '@docusaurus/plugin-content-docs';
 
   export interface Props extends DocSidebarItemProps {
-    item: PropSidebarItemHtml;
+    readonly item: PropSidebarItemHtml;
   }
 
   export default function DocSidebarItemHtml(props: Props): JSX.Element;
@@ -291,7 +333,7 @@ declare module '@theme/DocSidebarItem/Category' {
   import type {PropSidebarItemCategory} from '@docusaurus/plugin-content-docs';
 
   export interface Props extends DocSidebarItemProps {
-    item: PropSidebarItemCategory;
+    readonly item: PropSidebarItemCategory;
   }
 
   export default function DocSidebarItemCategory(props: Props): JSX.Element;
@@ -350,7 +392,7 @@ declare module '@theme/Footer/Logo' {
   import type {FooterLogo} from '@docusaurus/theme-common';
 
   export interface Props {
-    logo: FooterLogo;
+    readonly logo: FooterLogo;
   }
 
   export default function FooterLogo(props: Props): JSX.Element;
@@ -358,7 +400,7 @@ declare module '@theme/Footer/Logo' {
 
 declare module '@theme/Footer/Copyright' {
   export interface Props {
-    copyright: string;
+    readonly copyright: string;
   }
 
   export default function FooterCopyright(props: Props): JSX.Element;
@@ -368,7 +410,7 @@ declare module '@theme/Footer/LinkItem' {
   import type {FooterLinkItem} from '@docusaurus/theme-common';
 
   export interface Props {
-    item: FooterLinkItem;
+    readonly item: FooterLinkItem;
   }
 
   export default function FooterLinkItem(props: Props): JSX.Element;
@@ -378,10 +420,10 @@ declare module '@theme/Footer/Layout' {
   import type {ReactNode} from 'react';
 
   export interface Props {
-    style: 'light' | 'dark';
-    links: ReactNode;
-    logo: ReactNode;
-    copyright: ReactNode;
+    readonly style: 'light' | 'dark';
+    readonly links: ReactNode;
+    readonly logo: ReactNode;
+    readonly copyright: ReactNode;
   }
 
   export default function FooterLayout(props: Props): JSX.Element;
@@ -391,7 +433,7 @@ declare module '@theme/Footer/Links' {
   import type {Footer} from '@docusaurus/theme-common';
 
   export interface Props {
-    links: Footer['links'];
+    readonly links: Footer['links'];
   }
 
   export default function FooterLinks(props: Props): JSX.Element;
@@ -401,7 +443,7 @@ declare module '@theme/Footer/Links/MultiColumn' {
   import type {MultiColumnFooter} from '@docusaurus/theme-common';
 
   export interface Props {
-    columns: MultiColumnFooter['links'];
+    readonly columns: MultiColumnFooter['links'];
   }
 
   export default function FooterLinksMultiColumn(props: Props): JSX.Element;
@@ -411,7 +453,7 @@ declare module '@theme/Footer/Links/Simple' {
   import type {SimpleFooter} from '@docusaurus/theme-common';
 
   export interface Props {
-    links: SimpleFooter['links'];
+    readonly links: SimpleFooter['links'];
   }
 
   export default function FooterLinksSimple(props: Props): JSX.Element;
@@ -423,7 +465,7 @@ declare module '@theme/Heading' {
   type HeadingType = 'h1' | 'h2' | 'h3' | 'h4' | 'h5' | 'h6';
 
   export interface Props extends ComponentProps<HeadingType> {
-    as: HeadingType;
+    readonly as: HeadingType;
   }
 
   export default function Heading(props: Props): JSX.Element;
@@ -625,9 +667,9 @@ declare module '@theme/Navbar/MobileSidebar/Layout' {
   import type {ReactNode} from 'react';
 
   interface Props {
-    header: ReactNode;
-    primaryMenu: ReactNode;
-    secondaryMenu: ReactNode;
+    readonly header: ReactNode;
+    readonly primaryMenu: ReactNode;
+    readonly secondaryMenu: ReactNode;
   }
 
   export default function NavbarMobileSidebarLayout(props: Props): JSX.Element;
diff --git a/packages/docusaurus-theme-classic/src/theme/DocPage/index.tsx b/packages/docusaurus-theme-classic/src/theme/DocPage/index.tsx
index 2c908cc05535..32a226270459 100644
--- a/packages/docusaurus-theme-classic/src/theme/DocPage/index.tsx
+++ b/packages/docusaurus-theme-classic/src/theme/DocPage/index.tsx
@@ -34,7 +34,7 @@ function extractDocRouteMetadata(props: Props): null | {
     versionMetadata,
     location,
   } = props;
-  const currentDocRoute = docRoutes.find((docRoute) =>
+  const currentDocRoute = docRoutes!.find((docRoute) =>
     matchPath(location.pathname, docRoute),
   );
   if (!currentDocRoute) {
diff --git a/website/tsconfig.json b/website/tsconfig.json
index 2e797c69f685..96c58c1bae33 100644
--- a/website/tsconfig.json
+++ b/website/tsconfig.json
@@ -7,8 +7,9 @@
     "resolveJsonModule": true,
     "strict": true,
     // This is important. We run `yarn tsc` in website so we can catch issues
-    // with our declaration files (mostly name that are forgotten to be
-    // imported). Removing this would make things harder to catch.
+    // with our declaration files (mostly names that are forgotten to be
+    // imported, invalid semantics...). Because we don't have end-to-end type
+    // tests, removing this would make things much harder to catch.
     "skipLibCheck": false,
     "types": ["@types/jest"]
   },