A lightweight React hook for connecting to Model Context Protocol (MCP) servers. Simplifies authentication and tool calling for AI systems implementing the MCP standard.

Try it out: Chat Demo | MCP Inspector | Cloudflare Workers AI Playground

Installation

npm install use-mcp
# or
pnpm add use-mcp
# or
yarn add use-mcp

Development

To run the development environment with all examples and servers:

pnpm dev

This starts:

• Inspector: http://localhost:5001 - MCP server debugging tool
• Chat UI: http://localhost:5002 - Example chat interface
• Hono MCP Server: http://localhost:5101 - Example MCP server
• CF Agents MCP Server: http://localhost:5102 - Cloudflare Workers AI MCP server

Testing

Integration tests are located in the test/ directory and run headlessly by default:

cd test && pnpm test              # Run tests headlessly (default)
cd test && pnpm test:headed       # Run tests with visible browser
cd test && pnpm test:watch        # Run tests in watch mode
cd test && pnpm test:ui           # Run tests with interactive UI

Features

• 🔄 Automatic connection management with reconnection and retries
• 🔐 OAuth authentication flow handling with popup and fallback support
• 📦 Simple React hook interface for MCP integration
• 🧰 Full support for MCP tools, resources, and prompts
• 📄 Access server resources and read their contents
• 💬 Use server-provided prompt templates
• 🧰 TypeScript types for editor assistance and type checking
• 📝 Comprehensive logging for debugging
• 🌐 Works with both HTTP and SSE (Server-Sent Events) transports
• 🧠 Server-driven elicitation support with opt-in handler registration

Quick Start

import { useEffect } from 'react'
import { useMcp } from 'use-mcp/react'

function MyAIComponent() {
  const {
    state,          // Connection state: 'discovering' | 'pending_auth' | 'authenticating' | 'connecting' | 'loading' | 'ready' | 'failed'
    tools,          // Available tools from MCP server
    resources,      // Available resources from MCP server
    prompts,        // Available prompts from MCP server
    error,          // Error message if connection failed
    callTool,       // Function to call tools on the MCP server
    readResource,   // Function to read resource contents
    getPrompt,      // Function to get prompt messages
    retry,          // Retry connection manually
    authenticate,   // Manually trigger authentication
    clearStorage,   // Clear stored tokens and credentials
    onEliciation,   // Register handler for server elicitations
  } = useMcp({
    url: 'https://your-mcp-server.com',
    clientName: 'My App',
    autoReconnect: true,
  })

  useEffect(() => {
    if (state !== 'ready') return
    onEliciation(async params => {
      if (params.prompt === 'confirm-action') {
        return { action: 'respond', content: { type: 'text', text: 'Approved' } }
      }
      return { action: 'decline' }
    })
  }, [state, onEliciation])

  // Handle different states
  if (state === 'failed') {
    return (
      <div>
        <p>Connection failed: {error}</p>
        <button onClick={retry}>Retry</button>
        <button onClick={authenticate}>Authenticate Manually</button>
      </div>
    )
  }

  if (state !== 'ready') {
    return <div>Connecting to AI service...</div>
  }

  // Use available tools
  const handleSearch = async () => {
    try {
      const result = await callTool('search', { query: 'example search' })
      console.log('Search results:', result)
    } catch (err) {
      console.error('Tool call failed:', err)
    }
  }

  return (
    <div>
      <h2>Available Tools: {tools.length}</h2>
      <ul>
        {tools.map(tool => (
          <li key={tool.name}>{tool.name}</li>
        ))}
      </ul>
      <button onClick={handleSearch}>Search</button>
      
      {/* Example: Display and read resources */}
      {resources.length > 0 && (
        <div>
          <h3>Resources: {resources.length}</h3>
          <button onClick={async () => {
            const content = await readResource(resources[0].uri)
            console.log('Resource content:', content)
          }}>
            Read First Resource
          </button>
        </div>
      )}
      
      {/* Example: Use prompts */}
      {prompts.length > 0 && (
        <div>
          <h3>Prompts: {prompts.length}</h3>
          <button onClick={async () => {
            const result = await getPrompt(prompts[0].name)
            console.log('Prompt messages:', result.messages)
          }}>
            Get First Prompt
          </button>
        </div>
      )}
    </div>
  )
}

Setting Up OAuth Callback

To handle the OAuth authentication flow, you need to set up a callback endpoint in your app.

With React Router

// App.tsx with React Router
import { BrowserRouter as Router, Routes, Route } from 'react-router-dom'
import { useEffect } from 'react'
import { onMcpAuthorization } from 'use-mcp'

function OAuthCallback() {
  useEffect(() => {
    onMcpAuthorization()
  }, [])

  return (
    <div>
      <h1>Authenticating...</h1>
      <p>This window should close automatically.</p>
    </div>
  )
}

function App() {
  return (
    <Router>
      <Routes>
        <Route path="/oauth/callback" element={<OAuthCallback />} />
        <Route path="/" element={<YourMainComponent />} />
      </Routes>
    </Router>
  )
}

With Next.js Pages Router

// pages/oauth/callback.tsx
import { useEffect } from 'react'
import { onMcpAuthorization } from 'use-mcp'

export default function OAuthCallbackPage() {
  useEffect(() => {
    onMcpAuthorization()
  }, [])

  return (
    <div>
      <h1>Authenticating...</h1>
      <p>This window should close automatically.</p>
    </div>
  )
}

API Reference

useMcp Hook

function useMcp(options: UseMcpOptions): UseMcpResult

Options

Option	Type	Description
url	string	Required. URL of your MCP server
clientName	string	Name of your client for OAuth registration
clientUri	string	URI of your client for OAuth registration
callbackUrl	string	Custom callback URL for OAuth redirect (defaults to /oauth/callback on the current origin)
storageKeyPrefix	string	Storage key prefix for OAuth data in localStorage (defaults to "mcp:auth")
clientConfig	object	Custom configuration for the MCP client identity
debug	boolean	Whether to enable verbose debug logging
autoRetry	boolean | number	Auto retry connection if initial connection fails, with delay in ms
autoReconnect	boolean | number	Auto reconnect if an established connection is lost, with delay in ms (default: 3000)
transportType	'auto' | 'http' | 'sse'	Transport type preference: 'auto' (HTTP with SSE fallback), 'http' (HTTP only), 'sse' (SSE only) (default: 'auto')
preventAutoAuth	boolean	Prevent automatic authentication popup on initial connection (default: false)
onPopupWindow	(url: string, features: string, window: Window | null) => void	Callback invoked just after the authentication popup window is opened

Return Value

Property	Type	Description
state	string	Current connection state: 'discovering', 'pending_auth', 'authenticating', 'connecting', 'loading', 'ready', 'failed'
tools	Tool[]	Available tools from the MCP server
resources	Resource[]	Available resources from the MCP server
resourceTemplates	ResourceTemplate[]	Available resource templates from the MCP server
prompts	Prompt[]	Available prompts from the MCP server
error	string | undefined	Error message if connection failed
authUrl	string | undefined	Manual authentication URL if popup is blocked
log	{ level: 'debug' | 'info' | 'warn' | 'error'; message: string; timestamp: number }[]	Array of log messages
callTool	(name: string, args?: Record<string, unknown>) => Promise<any>	Function to call a tool on the MCP server
listResources	() => Promise<void>	Refresh the list of available resources
readResource	(uri: string) => Promise<{ contents: Array<...> }>	Read the contents of a specific resource
listPrompts	() => Promise<void>	Refresh the list of available prompts
getPrompt	(name: string, args?: Record<string, string>) => Promise<{ messages: Array<...> }>	Get a specific prompt with optional arguments
retry	() => void	Manually attempt to reconnect
disconnect	() => void	Disconnect from the MCP server
authenticate	() => void	Manually trigger authentication
clearStorage	() => void	Clear all stored authentication data
onEliciation	(cb: (params) => Promise<ElicitResult> | ElicitResult) => void	Register a handler to respond to server elicitation requests

License

MIT