diff --git a/e2e/docs/.vuepress/plugins/foo/fooPlugin.ts b/e2e/docs/.vuepress/plugins/foo/fooPlugin.ts
index 93ef0c8cff..a6031278ff 100644
--- a/e2e/docs/.vuepress/plugins/foo/fooPlugin.ts
+++ b/e2e/docs/.vuepress/plugins/foo/fooPlugin.ts
@@ -1,8 +1,9 @@
+import type { Plugin } from 'vuepress/core'
 import { getDirname, path } from 'vuepress/utils'
 
 const __dirname = getDirname(import.meta.url)
 
-export const fooPlugin = {
+export const fooPlugin: Plugin = {
   name: 'test-plugin',
   clientConfigFile: path.resolve(
     __dirname,
diff --git a/packages/core/src/app/appInit.ts b/packages/core/src/app/appInit.ts
index 1db287fd28..95ce110178 100644
--- a/packages/core/src/app/appInit.ts
+++ b/packages/core/src/app/appInit.ts
@@ -9,6 +9,8 @@ const log = debug('vuepress:core/app')
  * Initialize a vuepress app
  *
  * Plugins should be used before initialization.
+ *
+ * @internal
  */
 export const appInit = async (app: App): Promise<void> => {
   log('init start')
diff --git a/packages/core/src/app/appPrepare.ts b/packages/core/src/app/appPrepare.ts
index f8d2585f50..15dd6986b7 100644
--- a/packages/core/src/app/appPrepare.ts
+++ b/packages/core/src/app/appPrepare.ts
@@ -18,6 +18,8 @@ const log = debug('vuepress:core/app')
  * - routes
  * - site data
  * - other files that generated by plugins
+ *
+ * @internal
  */
 export const appPrepare = async (app: App): Promise<void> => {
   log('prepare start')
diff --git a/packages/core/src/app/appUse.ts b/packages/core/src/app/appUse.ts
index df53e43cab..9c98443a39 100644
--- a/packages/core/src/app/appUse.ts
+++ b/packages/core/src/app/appUse.ts
@@ -4,6 +4,13 @@ import { resolvePluginObject } from './resolvePluginObject.js'
 
 const log = debug('vuepress:core/app')
 
+/**
+ * Use a plugin in vuepress app.
+ *
+ * Should be called before initialization.
+ *
+ * @internal
+ */
 export const appUse = (app: App, rawPlugin: Plugin): App => {
   const pluginObject = resolvePluginObject(app, rawPlugin)
 
diff --git a/packages/core/src/app/createBaseApp.ts b/packages/core/src/app/createBaseApp.ts
index dc2b2ecaf4..dc8b18750d 100644
--- a/packages/core/src/app/createBaseApp.ts
+++ b/packages/core/src/app/createBaseApp.ts
@@ -17,7 +17,11 @@ import { resolveAppWriteTemp } from './resolveAppWriteTemp.js'
 import { setupAppThemeAndPlugins } from './setupAppThemeAndPlugins.js'
 
 /**
- * Create vuepress app
+ * Create base vuepress app.
+ *
+ * Notice that the base app could not be used for dev nor build.
+ *
+ * It would be used for creating dev app or build app, or for testing.
  */
 export const createBaseApp = (config: AppConfig): App => {
   const options = resolveAppOptions(config)
diff --git a/packages/core/src/app/createBuildApp.ts b/packages/core/src/app/createBuildApp.ts
index 2bc29eddff..13e1651b8e 100644
--- a/packages/core/src/app/createBuildApp.ts
+++ b/packages/core/src/app/createBuildApp.ts
@@ -2,7 +2,7 @@ import type { AppConfig, BuildApp } from '../types/index.js'
 import { createBaseApp } from './createBaseApp.js'
 
 /**
- * Create vuepress build app
+ * Create vuepress build app.
  */
 export const createBuildApp = (config: AppConfig): BuildApp => {
   const app = createBaseApp(config) as BuildApp
diff --git a/packages/core/src/app/createDevApp.ts b/packages/core/src/app/createDevApp.ts
index 3a0f4003e6..3d21ea35ed 100644
--- a/packages/core/src/app/createDevApp.ts
+++ b/packages/core/src/app/createDevApp.ts
@@ -2,7 +2,7 @@ import type { AppConfig, DevApp } from '../types/index.js'
 import { createBaseApp } from './createBaseApp.js'
 
 /**
- * Create vuepress dev app
+ * Create vuepress dev app.
  */
 export const createDevApp = (config: AppConfig): DevApp => {
   const app = createBaseApp(config) as DevApp
diff --git a/packages/core/src/app/prepare/prepareClientConfigs.ts b/packages/core/src/app/prepare/prepareClientConfigs.ts
index 59bb1f5624..4636bd5556 100644
--- a/packages/core/src/app/prepare/prepareClientConfigs.ts
+++ b/packages/core/src/app/prepare/prepareClientConfigs.ts
@@ -2,6 +2,8 @@ import type { App } from '../../types/index.js'
 
 /**
  * Generate client configs temp file
+ *
+ * @internal
  */
 export const prepareClientConfigs = async (app: App): Promise<void> => {
   // plugin hook: clientConfigFile
diff --git a/packages/core/src/app/prepare/prepareSiteData.ts b/packages/core/src/app/prepare/prepareSiteData.ts
index c2749c0dc2..7121e72845 100644
--- a/packages/core/src/app/prepare/prepareSiteData.ts
+++ b/packages/core/src/app/prepare/prepareSiteData.ts
@@ -17,6 +17,8 @@ if (import.meta.hot) {
 
 /**
  * Generate site data temp file
+ *
+ * @internal
  */
 export const prepareSiteData = async (app: App): Promise<void> => {
   let content = `\
diff --git a/packages/core/src/app/resolveAppDir.ts b/packages/core/src/app/resolveAppDir.ts
index 5e78b9d344..18819dca9d 100644
--- a/packages/core/src/app/resolveAppDir.ts
+++ b/packages/core/src/app/resolveAppDir.ts
@@ -6,6 +6,8 @@ const require = createRequire(import.meta.url)
 
 /**
  * Create directory util function
+ *
+ * @internal
  */
 export const createAppDirFunction =
   (baseDir: string): AppDirFunction =>
diff --git a/packages/core/src/app/resolveAppEnv.ts b/packages/core/src/app/resolveAppEnv.ts
index 7ec4bf96c0..d0b069c6a4 100644
--- a/packages/core/src/app/resolveAppEnv.ts
+++ b/packages/core/src/app/resolveAppEnv.ts
@@ -2,6 +2,8 @@ import type { AppEnv, AppOptions } from '../types/index.js'
 
 /**
  * Resolve environment flags for vuepress app
+ *
+ * @internal
  */
 export const resolveAppEnv = (options: AppOptions): AppEnv => ({
   isBuild: false,
diff --git a/packages/core/src/app/resolveAppMarkdown.ts b/packages/core/src/app/resolveAppMarkdown.ts
index 84ce7d0a1a..d3b35b4ef2 100644
--- a/packages/core/src/app/resolveAppMarkdown.ts
+++ b/packages/core/src/app/resolveAppMarkdown.ts
@@ -4,6 +4,8 @@ import type { App } from '../types/index.js'
 
 /**
  * Resolve markdown-it instance for vuepress app
+ *
+ * @internal
  */
 export const resolveAppMarkdown = async (app: App): Promise<Markdown> => {
   // plugin hook: extendsMarkdownOptions
diff --git a/packages/core/src/app/resolveAppOptions.ts b/packages/core/src/app/resolveAppOptions.ts
index 63b9379962..756227ffe5 100644
--- a/packages/core/src/app/resolveAppOptions.ts
+++ b/packages/core/src/app/resolveAppOptions.ts
@@ -6,6 +6,8 @@ const require = createRequire(import.meta.url)
 
 /**
  * Create app options with default values
+ *
+ * @internal
  */
 export const resolveAppOptions = ({
   // site config
diff --git a/packages/core/src/app/resolveAppPages.ts b/packages/core/src/app/resolveAppPages.ts
index d8cd00bd41..51ed100308 100644
--- a/packages/core/src/app/resolveAppPages.ts
+++ b/packages/core/src/app/resolveAppPages.ts
@@ -6,6 +6,8 @@ const log = debug('vuepress:core/app')
 
 /**
  * Resolve pages for vuepress app
+ *
+ * @internal
  */
 export const resolveAppPages = async (app: App): Promise<Page[]> => {
   log('resolveAppPages start')
diff --git a/packages/core/src/app/resolveAppSiteData.ts b/packages/core/src/app/resolveAppSiteData.ts
index 9f2b654e3e..bc37720131 100644
--- a/packages/core/src/app/resolveAppSiteData.ts
+++ b/packages/core/src/app/resolveAppSiteData.ts
@@ -4,6 +4,8 @@ import type { AppOptions, SiteData } from '../types/index.js'
  * Resolve site data for vuepress app
  *
  * Site data will also be used in client
+ *
+ * @internal
  */
 export const resolveAppSiteData = (options: AppOptions): SiteData => ({
   base: options.base,
diff --git a/packages/core/src/app/resolveAppVersion.ts b/packages/core/src/app/resolveAppVersion.ts
index 590340ffc4..5f356432a3 100644
--- a/packages/core/src/app/resolveAppVersion.ts
+++ b/packages/core/src/app/resolveAppVersion.ts
@@ -5,6 +5,8 @@ const require = createRequire(import.meta.url)
 
 /**
  * Resolve version of vuepress app
+ *
+ * @internal
  */
 export const resolveAppVersion = (): string => {
   const pkgJson = fs.readJsonSync(
diff --git a/packages/core/src/app/resolveAppWriteTemp.ts b/packages/core/src/app/resolveAppWriteTemp.ts
index f4e3b6c7d5..2a3560f072 100644
--- a/packages/core/src/app/resolveAppWriteTemp.ts
+++ b/packages/core/src/app/resolveAppWriteTemp.ts
@@ -3,6 +3,8 @@ import type { AppDir, AppWriteTemp } from '../types/index.js'
 
 /**
  * Resolve write temp file util for vuepress app
+ *
+ * @internal
  */
 export const resolveAppWriteTemp = (dir: AppDir): AppWriteTemp => {
   const writeTemp: AppWriteTemp = async (file: string, content: string) => {
diff --git a/packages/core/src/app/resolvePluginObject.ts b/packages/core/src/app/resolvePluginObject.ts
index 8ccdd72aaa..4636f48ac0 100644
--- a/packages/core/src/app/resolvePluginObject.ts
+++ b/packages/core/src/app/resolvePluginObject.ts
@@ -3,6 +3,8 @@ import type { App, Plugin, PluginObject } from '../types/index.js'
 
 /**
  * Resolve a plugin object according to name / path / module and config
+ *
+ * @internal
  */
 export const resolvePluginObject = <T extends PluginObject = PluginObject>(
   app: App,
diff --git a/packages/core/src/app/resolveThemeInfo.ts b/packages/core/src/app/resolveThemeInfo.ts
index 34e9ff3b0d..b16c371429 100644
--- a/packages/core/src/app/resolveThemeInfo.ts
+++ b/packages/core/src/app/resolveThemeInfo.ts
@@ -3,6 +3,8 @@ import { resolvePluginObject } from './resolvePluginObject.js'
 
 /**
  * Resolve theme info and its parent theme info
+ *
+ * @internal
  */
 export const resolveThemeInfo = (app: App, theme: Theme): ThemeInfo => {
   // resolve current theme info
diff --git a/packages/core/src/app/setupAppThemeAndPlugins.ts b/packages/core/src/app/setupAppThemeAndPlugins.ts
index f28c9f04e7..39aceda92b 100644
--- a/packages/core/src/app/setupAppThemeAndPlugins.ts
+++ b/packages/core/src/app/setupAppThemeAndPlugins.ts
@@ -3,6 +3,8 @@ import { resolveThemeInfo } from './resolveThemeInfo.js'
 
 /**
  * Setup theme and plugins for vuepress app
+ *
+ * @internal
  */
 export const setupAppThemeAndPlugins = (app: App, config: AppConfig): void => {
   // recursively resolve theme info
diff --git a/packages/core/src/page/createPage.ts b/packages/core/src/page/createPage.ts
index 600d60d63d..2e9946dec2 100644
--- a/packages/core/src/page/createPage.ts
+++ b/packages/core/src/page/createPage.ts
@@ -13,6 +13,9 @@ import { resolvePagePermalink } from './resolvePagePermalink.js'
 import { resolvePageRouteMeta } from './resolvePageRouteMeta.js'
 import { resolvePageSlug } from './resolvePageSlug.js'
 
+/**
+ * Create vuepress page object
+ */
 export const createPage = async (
   app: App,
   options: PageOptions,
diff --git a/packages/core/src/page/inferPagePath.ts b/packages/core/src/page/inferPagePath.ts
index 8d082ea93c..2a406c7b66 100644
--- a/packages/core/src/page/inferPagePath.ts
+++ b/packages/core/src/page/inferPagePath.ts
@@ -7,6 +7,8 @@ import type { App } from '../types/index.js'
 
 /**
  * Infer page path according to file path
+ *
+ * @internal
  */
 export const inferPagePath = ({
   app,
diff --git a/packages/core/src/page/parsePageContent.ts b/packages/core/src/page/parsePageContent.ts
index 8af9d92b96..03e036a87e 100644
--- a/packages/core/src/page/parsePageContent.ts
+++ b/packages/core/src/page/parsePageContent.ts
@@ -9,6 +9,8 @@ import type { App, PageFrontmatter, PageOptions } from '../types/index.js'
 
 /**
  * Render page content and extract related info
+ *
+ * @internal
  */
 export const parsePageContent = ({
   app,
diff --git a/packages/core/src/page/renderPageSfcBlocksToVue.ts b/packages/core/src/page/renderPageSfcBlocksToVue.ts
index 7428643823..79f15e92ca 100644
--- a/packages/core/src/page/renderPageSfcBlocksToVue.ts
+++ b/packages/core/src/page/renderPageSfcBlocksToVue.ts
@@ -2,6 +2,8 @@ import type { MarkdownSfcBlocks } from '@vuepress/markdown'
 
 /**
  * Render page sfc blocks to vue component
+ *
+ * @internal
  */
 export const renderPageSfcBlocksToVue = (
   sfcBlocks: MarkdownSfcBlocks,
diff --git a/packages/core/src/page/resolvePageChunkInfo.ts b/packages/core/src/page/resolvePageChunkInfo.ts
index 037018c6cc..0d5c6b994f 100644
--- a/packages/core/src/page/resolvePageChunkInfo.ts
+++ b/packages/core/src/page/resolvePageChunkInfo.ts
@@ -3,6 +3,8 @@ import type { App } from '../types/index.js'
 
 /**
  * Resolve page data file path
+ *
+ * @internal
  */
 export const resolvePageChunkInfo = ({
   app,
diff --git a/packages/core/src/page/resolvePageComponentInfo.ts b/packages/core/src/page/resolvePageComponentInfo.ts
index b1ee312cc4..1e5d4d6156 100644
--- a/packages/core/src/page/resolvePageComponentInfo.ts
+++ b/packages/core/src/page/resolvePageComponentInfo.ts
@@ -3,6 +3,8 @@ import type { App } from '../types/index.js'
 
 /**
  * Resolve page component and related info
+ *
+ * @internal
  */
 export const resolvePageComponentInfo = ({
   app,
diff --git a/packages/core/src/page/resolvePageContent.ts b/packages/core/src/page/resolvePageContent.ts
index c4bda0732b..51a1aa3ab2 100644
--- a/packages/core/src/page/resolvePageContent.ts
+++ b/packages/core/src/page/resolvePageContent.ts
@@ -9,6 +9,8 @@ const FALLBACK_CONTENT = ''
 
 /**
  * Resolve page content according to `content` or `filePath`
+ *
+ * @internal
  */
 export const resolvePageContent = async ({
   filePath,
diff --git a/packages/core/src/page/resolvePageDate.ts b/packages/core/src/page/resolvePageDate.ts
index d371062f68..f9b2d5312c 100644
--- a/packages/core/src/page/resolvePageDate.ts
+++ b/packages/core/src/page/resolvePageDate.ts
@@ -10,6 +10,8 @@ const DEFAULT_DATE = '0000-00-00'
  * Resolve page date according to frontmatter or file path
  *
  * It will be resolved as 'yyyy-MM-dd' format
+ *
+ * @internal
  */
 export const resolvePageDate = ({
   frontmatter,
diff --git a/packages/core/src/page/resolvePageFilePath.ts b/packages/core/src/page/resolvePageFilePath.ts
index ee5a1b01ed..32d34e23a5 100644
--- a/packages/core/src/page/resolvePageFilePath.ts
+++ b/packages/core/src/page/resolvePageFilePath.ts
@@ -3,6 +3,8 @@ import type { App, PageOptions } from '../types/index.js'
 
 /**
  * Resolve absolute and relative path of page file
+ *
+ * @internal
  */
 export const resolvePageFilePath = ({
   app,
diff --git a/packages/core/src/page/resolvePageHtmlInfo.ts b/packages/core/src/page/resolvePageHtmlInfo.ts
index 677921ed04..0417e4edbe 100644
--- a/packages/core/src/page/resolvePageHtmlInfo.ts
+++ b/packages/core/src/page/resolvePageHtmlInfo.ts
@@ -3,6 +3,8 @@ import type { App } from '../types/index.js'
 
 /**
  * Resolve page rendered html file path
+ *
+ * @internal
  */
 export const resolvePageHtmlInfo = ({
   app,
diff --git a/packages/core/src/page/resolvePageLang.ts b/packages/core/src/page/resolvePageLang.ts
index 3f2f243256..d0774e871c 100644
--- a/packages/core/src/page/resolvePageLang.ts
+++ b/packages/core/src/page/resolvePageLang.ts
@@ -3,6 +3,8 @@ import type { App, PageFrontmatter } from '../types/index.js'
 
 /**
  * Resolve language of page
+ *
+ * @internal
  */
 export const resolvePageLang = ({
   app,
diff --git a/packages/core/src/page/resolvePagePath.ts b/packages/core/src/page/resolvePagePath.ts
index c40e366455..0edac439de 100644
--- a/packages/core/src/page/resolvePagePath.ts
+++ b/packages/core/src/page/resolvePagePath.ts
@@ -3,6 +3,8 @@ import type { PageOptions } from '../types/index.js'
 
 /**
  * Resolve the final route path of a page
+ *
+ * @internal
  */
 export const resolvePagePath = ({
   permalink,
diff --git a/packages/core/src/page/resolvePagePermalink.ts b/packages/core/src/page/resolvePagePermalink.ts
index 15a421dec1..4b62c069f7 100644
--- a/packages/core/src/page/resolvePagePermalink.ts
+++ b/packages/core/src/page/resolvePagePermalink.ts
@@ -4,6 +4,8 @@ import type { App, PageFrontmatter } from '../types/index.js'
 
 /**
  * Resolve page permalink from frontmatter / options / pattern
+ *
+ * @internal
  */
 export const resolvePagePermalink = ({
   app,
diff --git a/packages/core/src/page/resolvePageRouteMeta.ts b/packages/core/src/page/resolvePageRouteMeta.ts
index 76e5030a91..fa66e39d36 100644
--- a/packages/core/src/page/resolvePageRouteMeta.ts
+++ b/packages/core/src/page/resolvePageRouteMeta.ts
@@ -2,6 +2,8 @@ import type { PageFrontmatter } from '../types/index.js'
 
 /**
  * Resolve page route meta
+ *
+ * @internal
  */
 export const resolvePageRouteMeta = ({
   frontmatter,
diff --git a/packages/core/src/page/resolvePageSlug.ts b/packages/core/src/page/resolvePageSlug.ts
index a7329ffbaa..f9c3704571 100644
--- a/packages/core/src/page/resolvePageSlug.ts
+++ b/packages/core/src/page/resolvePageSlug.ts
@@ -4,6 +4,8 @@ const DATE_RE = /(\d{4}-\d{1,2}(-\d{1,2})?)-(.*)/
 
 /**
  * Resolve page slug from filename
+ *
+ * @internal
  */
 export const resolvePageSlug = ({
   filePathRelative,
diff --git a/packages/core/src/pluginApi/createHookQueue.ts b/packages/core/src/pluginApi/createHookQueue.ts
index 09331eee3e..9fb70cc9ad 100644
--- a/packages/core/src/pluginApi/createHookQueue.ts
+++ b/packages/core/src/pluginApi/createHookQueue.ts
@@ -10,6 +10,8 @@ const log = debug('vuepress:core/plugin-api')
 
 /**
  * Create hook queue for plugin system
+ *
+ * @internal
  */
 export const createHookQueue = <T extends HooksName>(name: T): HookQueue<T> => {
   const items: HookItem<T>[] = []
diff --git a/packages/core/src/pluginApi/createPluginApi.ts b/packages/core/src/pluginApi/createPluginApi.ts
index 4f90cda435..18aa270ed7 100644
--- a/packages/core/src/pluginApi/createPluginApi.ts
+++ b/packages/core/src/pluginApi/createPluginApi.ts
@@ -2,6 +2,11 @@ import type { PluginApi } from '../types/index.js'
 import { createPluginApiHooks } from './createPluginApiHooks.js'
 import { createPluginApiRegisterHooks } from './createPluginApiRegisterHooks.js'
 
+/**
+ * Create vuepress plugin api
+ *
+ * @internal
+ */
 export const createPluginApi = (): PluginApi => {
   const plugins: PluginApi['plugins'] = []
   const hooks = createPluginApiHooks()
diff --git a/packages/core/src/pluginApi/createPluginApiHooks.ts b/packages/core/src/pluginApi/createPluginApiHooks.ts
index 0cefc33067..d8369985bb 100644
--- a/packages/core/src/pluginApi/createPluginApiHooks.ts
+++ b/packages/core/src/pluginApi/createPluginApiHooks.ts
@@ -1,6 +1,11 @@
 import type { PluginApi } from '../types/index.js'
 import { createHookQueue } from './createHookQueue.js'
 
+/**
+ * Create hooks for plugin api
+ *
+ * @internal
+ */
 export const createPluginApiHooks = (): PluginApi['hooks'] => ({
   // life cycle hooks
   onInitialized: createHookQueue('onInitialized'),
diff --git a/packages/core/src/pluginApi/createPluginApiRegisterHooks.ts b/packages/core/src/pluginApi/createPluginApiRegisterHooks.ts
index 79ee344016..22c94c4a01 100644
--- a/packages/core/src/pluginApi/createPluginApiRegisterHooks.ts
+++ b/packages/core/src/pluginApi/createPluginApiRegisterHooks.ts
@@ -2,6 +2,11 @@ import type { PluginApi } from '../types/index.js'
 import { normalizeAliasDefineHook } from './normalizeAliasDefineHook.js'
 import { normalizeClientConfigFileHook } from './normalizeClientConfigFileHook.js'
 
+/**
+ * Create registerHooks method for plugin api
+ *
+ * @internal
+ */
 export const createPluginApiRegisterHooks =
   (
     plugins: PluginApi['plugins'],
diff --git a/packages/core/src/pluginApi/normalizeAliasDefineHook.ts b/packages/core/src/pluginApi/normalizeAliasDefineHook.ts
index 6c3da1a21b..1b12ac361b 100644
--- a/packages/core/src/pluginApi/normalizeAliasDefineHook.ts
+++ b/packages/core/src/pluginApi/normalizeAliasDefineHook.ts
@@ -3,6 +3,8 @@ import type { AliasDefineHook } from '../types/index.js'
 
 /**
  * Normalize alias and define hook
+ *
+ * @internal
  */
 export const normalizeAliasDefineHook =
   (hook: AliasDefineHook['exposed']): AliasDefineHook['normalized'] =>
diff --git a/packages/core/src/pluginApi/normalizeClientConfigFileHook.ts b/packages/core/src/pluginApi/normalizeClientConfigFileHook.ts
index bba349702c..a6475852e4 100644
--- a/packages/core/src/pluginApi/normalizeClientConfigFileHook.ts
+++ b/packages/core/src/pluginApi/normalizeClientConfigFileHook.ts
@@ -4,6 +4,8 @@ import type { ClientConfigFileHook } from '../types/index.js'
 
 /**
  * Normalize hook for client config file
+ *
+ * @internal
  */
 export const normalizeClientConfigFileHook =
   (hook: ClientConfigFileHook['exposed']): ClientConfigFileHook['normalized'] =>
diff --git a/packages/core/src/types/app/options.ts b/packages/core/src/types/app/options.ts
index 4cbcabbc37..74a11478f6 100644
--- a/packages/core/src/types/app/options.ts
+++ b/packages/core/src/types/app/options.ts
@@ -9,18 +9,98 @@ import type { Theme } from '../theme.js'
  * Vuepress app common config that shared between dev and build
  */
 export interface AppConfigCommon extends Partial<SiteData> {
+  /**
+   * Source directory of the markdown files.
+   *
+   * Vuepress will load markdown files from this directory.
+   *
+   * @required
+   */
   source: string
+
+  /**
+   * Destination directory of the output files.
+   *
+   * Vuepress will output the static site files to this directory.
+   *
+   * @default `${source}/.vuepress/dist`
+   */
   dest?: string
+
+  /**
+   * Temp files directory.
+   *
+   * Vuepress will write temp files to this directory.
+   *
+   * @default `${source}/.vuepress/.temp`
+   */
   temp?: string
+
+  /**
+   * Cache files directory.
+   *
+   * Vuepress will write cache files to this directory.
+   *
+   * @default `${source}/.vuepress/.cache`
+   */
   cache?: string
+
+  /**
+   * Public files directory.
+   *
+   * Vuepress will copy the files from public directory to the output directory.
+   *
+   * @default `${source}/.vuepress/public`
+   */
   public?: string
 
+  /**
+   * Whether to enable debug mode
+   *
+   * @default false
+   */
   debug?: boolean
+
+  /**
+   * Markdown options
+   *
+   * @default {}
+   */
   markdown?: MarkdownOptions
+
+  /**
+   * Patterns to match the markdown files as pages
+   *
+   * @default ['**\/*.md', '!.vuepress', '!node_modules']
+   */
   pagePatterns?: string[]
+
+  /**
+   * Pattern to generate permalink for pages
+   *
+   * @default null
+   */
   permalinkPattern?: string | null
+
+  /**
+   * Vuepress bundler
+   *
+   * @required
+   */
   bundler: Bundler
+
+  /**
+   * Vuepress theme
+   *
+   * @required
+   */
   theme: Theme
+
+  /**
+   * Vuepress plugins
+   *
+   * @default []
+   */
   plugins?: PluginConfig
 }
 
@@ -87,17 +167,21 @@ export interface AppConfigBuild {
   /**
    * Specify the HTML template renderer to be used for build
    *
-   * @default templateRenderer from '@vuepress/utils'
+   * @default `import { templateRenderer } from '@vuepress/utils'`
    */
   templateBuildRenderer?: TemplateRenderer
 }
 
 /**
- * Vuepress app config
+ * Vuepress app user config.
+ *
+ * It would be provided by user, typically via a config file.
  */
 export type AppConfig = AppConfigBuild & AppConfigCommon & AppConfigDev
 
 /**
- * Vuepress app options
+ * Vuepress app options that resolved from user config.
+ *
+ * It fills all optional fields with a default value.
  */
 export type AppOptions = Required<AppConfig>
diff --git a/packages/core/src/types/app/utils.ts b/packages/core/src/types/app/utils.ts
index 0e70eb5508..fdfb3fd4a7 100644
--- a/packages/core/src/types/app/utils.ts
+++ b/packages/core/src/types/app/utils.ts
@@ -7,11 +7,34 @@ export type AppDirFunction = (...args: string[]) => string
  * Directory utils
  */
 export interface AppDir {
+  /**
+   * Resolve file path in cache directory
+   */
   cache: AppDirFunction
+
+  /**
+   * Resolve file path in temp directory
+   */
   temp: AppDirFunction
+
+  /**
+   * Resolve file path in source directory
+   */
   source: AppDirFunction
+
+  /**
+   * Resolve file path in dest directory
+   */
   dest: AppDirFunction
+
+  /**
+   * Resolve file path in public directory
+   */
   public: AppDirFunction
+
+  /**
+   * Resolve file path in client directory
+   */
   client: AppDirFunction
 }
 
diff --git a/packages/core/src/types/bundler.ts b/packages/core/src/types/bundler.ts
index cd3b8dc2a7..0f8e64fa78 100644
--- a/packages/core/src/types/bundler.ts
+++ b/packages/core/src/types/bundler.ts
@@ -8,8 +8,19 @@ import type { App } from './app/index.js'
  * - build: bundle assets for deployment
  */
 export interface Bundler {
+  /**
+   * Name of the bundler
+   */
   name: string
+
+  /**
+   * Method to run vuepress app in dev mode, starting dev server
+   */
   dev: (app: App) => Promise<() => Promise<void>>
+
+  /**
+   * Method to run vuepress app in build mode, generating static pages and assets
+   */
   build: (app: App) => Promise<void>
 }
 
diff --git a/packages/core/src/types/plugin.ts b/packages/core/src/types/plugin.ts
index ae52a6b334..99e65f7517 100644
--- a/packages/core/src/types/plugin.ts
+++ b/packages/core/src/types/plugin.ts
@@ -27,10 +27,14 @@ export type PluginFunction<T extends PluginObject = PluginObject> = (
  * Vuepress plugin object
  */
 export interface PluginObject extends Partial<HooksExposed> {
-  // plugin name
+  /**
+   * Name of the plugin
+   */
   name: string
 
-  // allow use a plugin multiple times or not
+  /**
+   * Allow the plugin to be used multiple times or not
+   */
   multiple?: boolean
 }