WebMCP Documentation

@mcp-b/extension-tools wraps Chrome Extension APIs as MCP tool classes. Each API is a dedicated class that handles permission checking, error formatting, and tool registration against an McpServer instance.

npm: @mcp-b/extension-tools
license: MIT
dependencies: @mcp-b/smart-dom-reader, @mcp-b/webmcp-ts-sdk, zod
peer: @types/chrome (dev)

Installation

npm install @mcp-b/extension-tools @modelcontextprotocol/sdk

Minimal example

Usage

import { TabsApiTools, BookmarksApiTools, StorageApiTools } from '@mcp-b/extension-tools';
import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';

const server = new McpServer({
  name: 'chrome-extension-server',
  version: '1.0.0',
});

const tabsTools = new TabsApiTools(server, {
  listActiveTabs: true,
  createTab: true,
  closeTabs: true,
});
tabsTools.register();

const bookmarksTools = new BookmarksApiTools(server, {
  getBookmarks: true,
  createBookmark: true,
});
bookmarksTools.register();

Each tool class constructor takes two arguments:

An McpServer instance
An options object where each key corresponds to a tool method. Set a key to true to register that tool, or false (or omit it) to skip it.

BaseApiTools

All API tool classes extend BaseApiTools<TOptions>:

abstract class BaseApiTools<TOptions> {
  protected abstract apiName: string;

  constructor(server: McpServer, options: TOptions);

  abstract checkAvailability(): ApiAvailability;
  abstract registerTools(): void;

  register(): void;

  protected shouldRegisterTool(toolName: string): boolean;
  protected formatError(error: unknown): CallToolResult;
  protected formatSuccess(message: string, data?: unknown): CallToolResult;
  protected formatJson(data: unknown): CallToolResult;
}

Method	Description
`register()`	Checks API availability, then calls `registerTools()` if available
`checkAvailability()`	Returns `{ available: boolean, message: string }`
`shouldRegisterTool(name)`	Returns `false` if the option for that tool is explicitly `false`
`formatError(error)`	Wraps an error into a structured `CallToolResult` with `isError: true`
`formatSuccess(message, data?)`	Returns a success `CallToolResult` with optional JSON data

Available API tool classes (62)

Each class name follows the pattern <ApiName>ApiTools. The table below lists all implemented classes grouped by category.

Core browser

Class	Chrome Permission	Description
`TabsApiTools`	`tabs`	Create, update, query, close, group, move tabs
`WindowsApiTools`	(none)	Control browser windows
`TabGroupsApiTools`	`tabGroups`	Manage tab groups
`BookmarksApiTools`	`bookmarks`	CRUD operations on bookmarks
`HistoryApiTools`	`history`	Search and manage browsing history
`SessionsApiTools`	`sessions`	Query and restore browser sessions
`TopSitesApiTools`	`topSites`	Access most-visited sites
`ReadingListApiTools`	`readingList`	Access the reading list

Content and scripting

Class	Chrome Permission	Description
`ScriptingApiTools`	`scripting`	Execute scripts and inject CSS
`UserScriptsApiTools`	`userScripts`	Execute user scripts
`DomApiTools`	(none)	Access DOM from extensions
`ContentSettingsApiTools`	`contentSettings`	Manage content settings
`DeclarativeContentApiTools`	`declarativeContent`	Take actions based on page content

Storage and data

Class	Chrome Permission	Description
`StorageApiTools`	`storage`	Get, set, remove, clear extension storage (local, sync, session)
`CookiesApiTools`	`cookies`	Manage browser cookies
`BrowsingDataApiTools`	`browsingData`	Clear browsing data

Network

Class	Chrome Permission	Description
`WebRequestApiTools`	`webRequest`	Intercept and modify requests
`WebNavigationApiTools`	`webNavigation`	Monitor web navigation events
`DeclarativeNetRequestApiTools`	`declarativeNetRequest`	Modify network requests declaratively
`ProxyApiTools`	`proxy`	Manage proxy settings

Downloads and capture

Class	Chrome Permission	Description
`DownloadsApiTools`	`downloads`	Control file downloads
`PageCaptureApiTools`	`pageCapture`	Save pages as MHTML
`TabCaptureApiTools`	`tabCapture`	Capture tab media streams
`DesktopCaptureApiTools`	`desktopCapture`	Capture desktop content

UI and interaction

Class	Chrome Permission	Description
`NotificationsApiTools`	`notifications`	Create system notifications
`OmniboxApiTools`	(none)	Customize the address bar
`ContextMenusApiTools`	`contextMenus`	Create context menu items
`SidePanelApiTools`	`sidePanel`	Control the side panel
`CommandsApiTools`	(none)	Manage keyboard shortcuts

DevTools

Class	Chrome Permission	Description
`DevtoolsInspectedWindowApiTools`	(none)	Interact with inspected window
`DevtoolsNetworkApiTools`	(none)	Retrieve network information
`DevtoolsPanelsApiTools`	(none)	Create DevTools panels

Identity and auth

Class	Chrome Permission	Description
`IdentityApiTools`	`identity`	OAuth2 authentication
`WebAuthenticationProxyApiTools`	`webAuthenticationProxy`	Web authentication proxy
`CertificateProviderApiTools`	`certificateProvider`	Provide certificates for TLS
`PlatformKeysApiTools`	`platformKeys`	Platform-specific keys

System

Class	Chrome Permission	Description
`AlarmsApiTools`	`alarms`	Set and manage alarms
`IdleApiTools`	`idle`	Detect idle state
`PowerApiTools`	`power`	Power management
`SystemCpuApiTools`	`system.cpu`	Query CPU information
`SystemMemoryApiTools`	`system.memory`	Get memory information
`SystemStorageApiTools`	`system.storage`	Query storage devices
`SystemLogApiTools`	`systemLog`	Add system log entries (ChromeOS)

Extension management

Class	Chrome Permission	Description
`RuntimeApiTools`	(none)	Access extension runtime information
`ExtensionApiTools`	(none)	Extension utilities
`ManagementApiTools`	`management`	Manage installed extensions
`PermissionsApiTools`	(none)	Request optional permissions at runtime
`OffscreenApiTools`	`offscreen`	Manage offscreen documents

Media and output

Class	Chrome Permission	Description
`AudioApiTools`	`audio`	Audio device management (ChromeOS)
`TtsApiTools`	`tts`	Text-to-speech
`TtsEngineApiTools`	`ttsEngine`	Implement a TTS engine
`FontSettingsApiTools`	`fontSettings`	Manage font settings
`PrintingApiTools`	`printing`	Print documents (ChromeOS)
`PrintingMetricsApiTools`	`printingMetrics`	Printing metrics (ChromeOS)

Internationalization and messaging

Class	Chrome Permission	Description
`I18nApiTools`	(none)	Internationalization utilities
`GcmApiTools`	`gcm`	Google Cloud Messaging
`InstanceIDApiTools`	(none)	Instance ID operations
`SearchApiTools`	`search`	Search via default provider

Enterprise and platform

Class	Chrome Permission	Description
`EnterpriseDeviceAttributesApiTools`	(policy required)	Access enterprise device attributes
`EnterpriseHardwarePlatformApiTools`	(policy required)	Access enterprise hardware info
`EnterpriseNetworkingAttributesApiTools`	(policy required)	Access enterprise network attributes
`EnterprisePlatformKeysApiTools`	(policy required)	Enterprise platform keys
`LoginStateApiTools`	`loginState`	Read login state (ChromeOS)
`VpnProviderApiTools`	`vpnProvider`	Implement VPN client (ChromeOS)
`WallpaperApiTools`	`wallpaper`	Set wallpaper (ChromeOS)
`DocumentScanApiTools`	`documentScan`	Scan documents (ChromeOS)
`InputImeApiTools`	(none)	Input method editor (ChromeOS)
`FileBrowserHandlerApiTools`	`fileBrowserHandler`	Handle file browser events (ChromeOS)
`FileSystemProviderApiTools`	`fileSystemProvider`	Provide file systems (ChromeOS)
`DebuggerApiTools`	`debugger`	Debug network and JavaScript

DOM extraction

Class	Chrome Permission	Description
`DomExtractionTools`	`scripting`	Token-efficient DOM extraction using `@mcp-b/smart-dom-reader`

Chrome API registry

The ChromeApi enum and CHROME_API_REGISTRY constant map every Chrome Extension API to its metadata:

interface ChromeApiMetadata {
  minChromeVersion?: number;
  platform: 'all' | 'chromeos';
  channel: 'stable' | 'dev';
  manifestVersions: (2 | 3)[];
  requiresPolicy: boolean;
  foregroundOnly: boolean;
  contexts: ('background' | 'content' | 'devtools' | 'all')[];
  namespace: string;
}

Helper functions:

Function	Description
`isApiAvailable(api, context, manifestVersion, platform?, chromeVersion?)`	Check if an API is available in the current context
`getAvailableApis(context, manifestVersion, platform?, chromeVersion?)`	Get all available APIs for a context
`getChromeApiReference(api)`	Get the runtime `chrome.*` object for an API

Permission requirements

Declare required permissions in your extension’s manifest.json. APIs like i18n, runtime, and extension work without explicit permissions. Enterprise APIs require force-install via enterprise policy.

{
  "manifest_version": 3,
  "permissions": ["tabs", "bookmarks", "storage", "scripting"],
  "host_permissions": ["<all_urls>"]
}

APIs under development (12)

The following APIs are not yet implemented: AccessibilityFeatures, Action, DevtoolsPerformance, DevtoolsRecorder, Dns, Events, ExtensionTypes, PrinterProvider, Privacy, Processes, SystemDisplay, Types.

@mcp-b/smart-dom-reader (DOM extraction used by DomExtractionTools)
@mcp-b/transports (browser MCP transports)
Chrome DevTools MCP (upstream DevTools Protocol bridge)

Packages

WebMCP standard

Core runtime

React

Tooling

@mcp-b/extension-tools

Installation

Minimal example

Usage

BaseApiTools

Available API tool classes (62)

Core browser

Content and scripting

Storage and data

Network

Downloads and capture

UI and interaction

DevTools

Identity and auth

System

Extension management

Media and output

Internationalization and messaging

Enterprise and platform

DOM extraction

Chrome API registry

Permission requirements

APIs under development (12)

​Installation

​Minimal example

​Usage

​BaseApiTools

​Available API tool classes (62)

​Core browser

​Content and scripting

​Storage and data

​Network

​Downloads and capture

​UI and interaction

​DevTools

​Identity and auth

​System

​Extension management

​Media and output

​Internationalization and messaging

​Enterprise and platform

​DOM extraction

​Chrome API registry

​Permission requirements

​APIs under development (12)

​Related

Installation

Minimal example

Usage

BaseApiTools

Available API tool classes (62)

Core browser

Content and scripting

Storage and data

Network

Downloads and capture

UI and interaction

DevTools

Identity and auth

System

Extension management

Media and output

Internationalization and messaging

Enterprise and platform

DOM extraction

Chrome API registry

Permission requirements

APIs under development (12)

Related