Tool Host - Universal MCP Agent Platform for VS Code

Transform your VS Code into an autonomous, agent-powered development environment. Tool Host acts as a universal MCP (Model Context Protocol) Host, enabling AI agents to leverage any tool, API, or data source through the Model Context Protocol ecosystem.

Features

Universal MCP Host

Connect Multiple MCP Servers: Manage and orchestrate multiple Model Context Protocol servers simultaneously
Tool Aggregation: Automatically aggregate tools, resources, and prompts from all connected servers
Auto-Restart & Health Tracking: Intelligent server lifecycle management with exponential backoff
Hot-Reload Configuration: Modify server configs without restarting VS Code

Autonomous AI Agent

Multi-LLM Support: Works with Anthropic Claude, OpenAI GPT, and OpenAI-compatible APIs (Ollama, LM Studio)
Reasoning Loop: Implements the REASON → ACT → OBSERVE pattern for autonomous task completion
Context-Aware: Automatically gathers VS Code context (active files, workspace, git status)
Human-in-the-Loop: Requires confirmation for destructive operations

Agent Modes

Ask Mode: Get answers and explanations without code changes
Code Mode: Generate and modify code to implement features
Architect Mode: Plan complex system designs and refactorings

Developer Experience

Real-Time Activity Panel: Watch your agent reason, plan, and execute tasks
Secure Credential Storage: API keys stored safely in VS Code's SecretStorage
Rich Tool Visualization: See tool inputs, outputs, and execution results
VS Code Native: Fully integrated with VS Code's UI and workflows

Installation

Install from the VS Code Marketplace (search for "Tool Host")

Or install manually:

code --install-extension toolhost-*.vsix

Quick Start

1. Configure Your LLM

Open the Command Palette (Cmd+Shift+P / Ctrl+Shift+P) and run:

Tool Host: Configure LLM Settings

Enter your API key and select your preferred model:

Anthropic: claude-3-5-sonnet-20241022 (recommended)
OpenAI: gpt-4-turbo-preview, gpt-4o
Custom: Any OpenAI-compatible endpoint (Ollama, LM Studio, etc.)

2. Add MCP Servers

Run:

Tool Host: Configure MCP Servers

Or manually edit your settings.json:

{
  "toolhost.mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "/path/to/workspace"]
    },
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": {
        "GITHUB_TOKEN": "your-token-here"
      }
    }
  }
}

3. Run Your Agent

Open the Command Palette and run:

Tool Host: Run Agent

Enter your goal, and watch the agent work!

Available Commands

Command	Description
`Tool Host: Run Agent`	Launch the autonomous agent with a goal
`Tool Host: Configure LLM Settings`	Set up your LLM provider and API key
`Tool Host: Configure MCP Servers`	Manage MCP server configurations
`Tool Host: Show Status`	Display health status of all MCP servers
`Tool Host: List Tools`	View all available tools from connected servers
`Tool Host: Show Agent Activity`	Open the agent activity panel
`Tool Host: Run MCP Diagnostics`	Validate connectivity and capabilities of each MCP server
`Tool Host: Clear Confirmation Preferences`	Reset saved confirmation preferences

Configuration

LLM Settings

{
  "toolhost.llmModel": "claude-3-5-sonnet-20241022",
  "toolhost.llmBaseUrl": "",  // Optional: for custom endpoints
  "toolhost.llmTemperature": 0.7,
  "toolhost.llmMaxTokens": 4096
}

MCP Server Configuration

Each server configuration supports:

command: Executable command (e.g., node, python, npx)
args: Command-line arguments
env: Environment variables for the server process

Testing

Prerequisites (Linux / WSL)

VS Code integration tests require a handful of system libraries. Install them once per environment:

sudo apt-get update
sudo apt-get install -y libnspr4 libnss3 libatk-bridge2.0-0 libxkbcommon0 libx11-xcb1 libgtk-3-0 libxshmfence1 libgbm1

Commands

npm run lint          # ESLint
npm run check-types   # TypeScript type checking
npm run compile       # Build extension bundle
npm run test          # Runs compile/lint + VS Code integration tests

Packaging & Release

Bump the version in package.json and update CHANGELOG.md.
Rebuild the extension: npm run compile.
Package for the marketplace: npx vsce package.
Test the generated .vsix locally (code --install-extension toolhost-*.vsix).
Publish with npx vsce publish (requires a VS Marketplace token).

cwd: Working directory
stderr: How to handle stderr (inherit, ignore, or pipe)
autoRestart: Enable automatic restart on crash (default: true)
maxRestarts: Maximum restart attempts (default: 3)

🌟 Example Use Cases

Code Generation

"Create a REST API endpoint for user authentication with JWT tokens"

Debugging

"Find and fix the bug causing the null pointer exception in UserService.ts"

Refactoring

"Refactor this component to use React hooks instead of class components"

Documentation

"Generate JSDoc comments for all public methods in this file"

🔌 Compatible MCP Servers

Tool Host works with any MCP-compliant server. Popular options:

@modelcontextprotocol/server-filesystem: File system operations
@modelcontextprotocol/server-github: GitHub API integration
@modelcontextprotocol/server-postgres: PostgreSQL database access
@modelcontextprotocol/server-brave-search: Web search
And many more from the MCP servers repository

🏗️ Architecture

Tool Host follows a three-layer architecture:

Extension Layer (extension.ts): VS Code integration and command registration
MCP Host Manager (McpHost.ts): Manages multiple MCP server connections
Agent Engine (Agent.ts): Reasoning and execution with REASON→ACT→OBSERVE loop

See CLAUDE.md for detailed architecture documentation.

🤝 Contributing

Contributions are welcome! Please see our contributing guidelines.

Fork the repository
Create a feature branch
Make your changes
Submit a pull request

📄 License

MIT License - see LICENSE for details.

🐛 Known Issues

Server config changes require add/remove to trigger restart (config hash comparison needed)
No timeout wrapper for MCP operations
Duplicate tool names from multiple servers not warned in UI

📚 Resources

🙏 Acknowledgments

Built with the Model Context Protocol SDK by Anthropic.

Made with ❤️ for the AI coding community