MCP WireView

A VSCode extension for visualizing MCP (Model Context Protocol) messages with an interactive JSON viewer.

Features

• 🔌 Connect to MCP Servers - Configure and connect to remote MCP servers via HTTP
• 🎨 Rich JSON Visualization - Interactive JSON viewer powered by react-json-tree (same as Redux DevTools)
• 📡 Real-time Streaming - Full support for Server-Sent Events (SSE) streaming responses
• 🎯 Session State Tracking - Clear visual indicators for connection and initialization status
• 🌓 Theme Integration - Automatic adaptation to VSCode light/dark themes
• 📝 Complete Protocol Support - Initialize, list tools/prompts/resources, call tools, and custom requests

Installation

From VSIX (Local Development)

1. Download the .vsix file
2. Open VSCode
3. Go to Extensions view (Ctrl+Shift+X)
4. Click "..." menu → "Install from VSIX..."
5. Select the downloaded .vsix file

Usage

1. Configure MCP Server URL

Set your MCP server URL via:

Option A: Command Palette

• Press Ctrl+Shift+P
• Run "MCP: Set Server URL"
• Enter your server URL (e.g., http://localhost:3000/mcp)

Option B: Status Bar

• Click the MCP status indicator in the status bar
• Enter your server URL

Option C: Settings

• Open Settings (Ctrl+,)
• Search for "MCP WireView"
• Set "MCP Client: Server Url"

2. Initialize Session

• Press Ctrl+Shift+P
• Run "MCP: Send Initialize Request"
• View the response in the interactive webview

3. Explore MCP Resources

List available tools:

Command: MCP: List Tools

List available prompts:

Command: MCP: List Prompts

List available resources:

Command: MCP: List Resources

4. Call a Tool

• Run "MCP: Call Tool"
• Enter tool name
• Enter arguments as JSON object (e.g., {"param": "value"})
• View the response in the webview

5. Send Custom Requests

• Run "MCP: Send Custom JSON Request"
• Enter a JSON-RPC request:

  {"method": "tools/list", "params": {}}

Session States

The status bar displays the current MCP session state:

State	Icon	Description
URL Not Set	$(debug-disconnect)	No server URL configured
Uninitialized	$(sync~spin)	Server URL set but not initialized
Initialized	$(check)	Session initialized and ready

Commands

Command	Description
MCP: Set Server URL	Configure the MCP server URL
MCP: Send Initialize Request	Initialize the MCP session
MCP: Uninitialize	Reset the session (keeps URL)
MCP: List Tools	List available tools
MCP: List Prompts	List available prompts
MCP: List Resources	List available resources
MCP: Call Tool	Execute a tool with arguments
MCP: Send Custom JSON Request	Send a custom JSON-RPC request

Configuration

Setting	Type	Default	Description
mcp.serverURL	string	""	URL of the MCP server to connect to

Webview Features

The interactive webview provides:

• Collapsible JSON nodes - Click to expand/collapse objects and arrays
• Syntax highlighting - Color-coded JSON with VSCode theme integration
• Request/Response display - See both sides of the communication
• SSE event visualization - View all streaming events with event count
• Error handling - Clear error messages with context

Development

Prerequisites

• Node.js 20.x or higher
• npm

Setup

# Install dependencies
npm install

# Install webview dependencies
npm run install:webview

# Compile
npm run compile

Build Commands

# Compile both extension and webview
npm run compile

# Compile extension only
npm run compile:extension

# Compile webview only
npm run compile:webview

# Watch extension (auto-recompile on changes)
npm run watch

# Watch webview (Vite dev server)
npm run watch:webview

Testing

1. Open this folder in VSCode
2. Press F5 to launch Extension Development Host
3. In the new window, use the MCP commands
4. Open "MCP WireView" output channel for logs
5. Right-click webview → "Open Webview Developer Tools" for debugging

Architecture

Extension (TypeScript)

• src/extension.ts - Entry point
• src/commands.ts - Command handlers
• src/mcpClient.ts - HTTP client with SSE support
• src/responseViewer.ts - Webview manager

Webview UI (React + TypeScript)

• src/webview-ui/src/App.tsx - Root component
• src/webview-ui/src/components/ - UI components
• src/webview-ui/src/theme/ - VSCode theme integration
• Build tool: Vite

MCP Protocol Support

• Protocol Version: 2025-06-18
• Transport: HTTP POST with JSON-RPC 2.0
• Streaming: Server-Sent Events (SSE)
• Capabilities: roots, sampling, elicitation

License

MIT

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Links

• MCP Specification
• VSCode Extension API
• react-json-tree