Simple Mcp Client

Simple MCP Client

A full-stack chat application that connects to LLM providers and utilizes tools from MCP (Model Context Protocol) servers. Features a clean, modern interface with comprehensive tool execution and visualization capabilities.

Current State

This application is fully functional and production-ready with robust error handling:

✅ Complete Tool Execution Pipeline: End-to-end tool calling with LLM follow-up responses ✅ Smart Error Recovery: Automatic parameter correction for any MCP server validation errors ✅ Robust Error Handling: Comprehensive tool failure recovery and OpenAI API compliance ✅ Professional UI: Collapsible tool call displays with real-time status indicators ✅ Multi-LLM Support: OpenAI, Gemini, and Bedrock compatible APIs ✅ MCP Server Management: Remote and local MCP server support with process management ✅ Real-time Status: Live connection status and server health monitoring ✅ Dark/Light Mode: Persistent theme switching with clean design ✅ Chat Management: Clear chat functionality with message history ✅ Conversation History: Proper OpenAI API compliance for multi-turn tool conversations ✅ Retry Mechanisms: Intelligent retry logic for validation errors with parameter correction

Features

• Modern Chat Interface: Clean UI with markdown support and user/assistant message bubbles
• Complete Tool Execution: Tools are executed with results fed back to LLM for natural responses
• Tool Visualization: Expandable tool call displays showing request/response details with status indicators
• Advanced Error Handling: Automatic recovery from tool failures with intelligent parameter correction
• OpenAI API Compliance: Proper conversation history management for multi-turn tool interactions
• MCP Server Integration: Connect and manage multiple MCP servers with automatic tool discovery
• Local & Remote Servers: Support for both HTTP-based and local process-based MCP servers
• Process Management: Automatic server startup/shutdown with health monitoring
• Multi-LLM Support: OpenAI, Gemini, and Bedrock compatible APIs
• Real-time Updates: Live connection status and server management
• Responsive Design: Works on desktop and mobile devices
• Universal MCP Compatibility: Works with any MCP server through generic error parsing

Tech Stack

• Frontend: React + TypeScript + Vite
• UI Library: Shadcn/ui + Tailwind CSS + Lucide Icons
• State Management: Zustand
• Backend: FastAPI + Python 3.8+
• Database: SQLite (file-based)
• Protocol: MCP over JSON-RPC 2.0 (HTTP and stdio)
• Markdown: ReactMarkdown for rich message rendering

Quick Start

1. Automated Setup (Recommended)

Run the setup script from the project root:

./setup.sh

This script will:

• Check system prerequisites (Python 3.8+, Node.js 16+, npm)
• Create and configure Python virtual environment
• Install all Python dependencies
• Install all Node.js dependencies
• Initialize the database
• Provide clear instructions for starting the application

2. Quick Development Startup (Recommended)

The application supports multiple deployment environments. Use the unified start script to run both backend and frontend:

Local Development (Default)

./start-dev.sh
# or: ./start-dev.sh local

Workshop/Kubernetes Environments (Instruqt, etc.)

When the backend isn't accessible via localhost, use proxy mode:

./start-dev.sh proxy

This proxies API requests through the frontend dev server to avoid external port access issues.

Custom Backend URL

For remote backends or custom deployments:

./start-dev.sh custom https://your-backend-url/api
# or: VITE_API_BASE_URL=https://your-backend-url/api ./start-dev.sh custom

Quick Reference - Start Options

| Command | Use Case | Description | |---------|----------|-------------| | ./start-dev.sh | Local development | Default mode, both servers on localhost | | ./start-dev.sh proxy | Workshops, Kubernetes | Frontend proxies API requests | | ./start-dev.sh custom URL | Remote backends | Custom backend URL |

The script will:

• Start backend server on http://localhost:8002
• Start frontend server on http://localhost:5173 (or next available port)
• Log all output to logs/backend.log and logs/frontend.log
• Handle graceful shutdown when you press Ctrl+C
• Display real-time status and URLs

To stop the servers: Press Ctrl+C in the terminal running the script.

Monitor logs in real-time:

# Backend logs
tail -f logs/backend.log

# Frontend logs  
tail -f logs/frontend.log

3. Manual Setup

If you prefer manual setup or need to troubleshoot:

Backend Setup

1. Navigate to the backend directory:

``bash cd backend ``

1. Create a Python virtual environment:

``bash python -m venv venv source venv/bin/activate # On Windows: venv\Scripts\activate ``

1. Install dependencies:

``bash pip install -r requirements.txt ``

1. Start the FastAPI server:

``bash python main.py ``

The API will be available at http://localhost:8002

Frontend Setup

1. Navigate to the frontend directory:

``bash cd frontend ``

1. Install dependencies:

``bash npm install ``

1. Start the development server:

``bash npm run dev ``

The app will be available at http://localhost:5173

Usage

Getting Started

1. Configure an LLM Provider:

• Click the Settings icon in the top-right
• Add your LLM provider (OpenAI, Gemini, or Bedrock)
• Enter your API key and configure settings
• The status indicator will turn green when connected

1. Add MCP Servers (Optional):

• In Settings, go to the MCP Servers section
• Add remote or local MCP servers
• Start servers and verify tool discovery
• Tools will be automatically available to the LLM

1. Start Chatting:

• Go back to the Chat interface
• Ask questions or request tool usage
• Watch tools execute in collapsible displays
• Get natural language responses based on tool results

Example Interactions

• "What's the weather in New York?" - Uses weather MCP tools
• "Search for information about..." - Uses search/web MCP tools
• "Analyze this data..." - Uses analysis MCP tools
• General conversation - Direct LLM responses without tools

Configuration

LLM Providers

The application supports multiple LLM providers:

• OpenAI-Compatible:
• OpenAI API
• Local models (Ollama, LM Studio, etc.)
• Other OpenAI-compatible endpoints
• Google Gemini: Direct Gemini API integration
• AWS Bedrock: Claude, Titan, and other Bedrock models

MCP Servers

Two types of MCP servers are supported:

Remote MCP Servers (HTTP)

Connect to HTTP-based MCP servers:

• Name: Display name for the server
• URL: HTTP endpoint for JSON-RPC communication
• API Key: Optional authentication token
• Automatic Discovery: Tools are discovered on connection

Local MCP Servers (Process)

Run MCP servers as local processes:

• Name: Display name for the server
• Command: Executable command (e.g., uv, npx, python)
• Arguments: Command arguments (one per line)
• Working Directory: Optional directory to run the command in
• Auto-start: Whether to start the server automatically
• Process Management: Automatic startup, health monitoring, and cleanup

Example Local Server Configuration:

Name: Weather Server
Command: uv
Arguments: 
  run
  weather.py
Working Directory: /path/to/weather-mcp/weather
Auto-start: Yes

Security Note

⚠️ This is a demo application designed for development and testing purposes. Current security considerations:

• API keys are stored with basic hashing (not production-ready encryption)
• No authentication/authorization system implemented
• Local MCP servers run with user permissions
• CORS enabled for development (localhost only)
• Comprehensive logging may expose sensitive data in development mode

For production use, implement:

• Proper encryption for sensitive data storage
• User authentication and session management
• API rate limiting and input validation
• Secure MCP server sandboxing
• Database access controls
• Audit and sanitize all logging output

See CLAUDE.md for detailed security improvement tasks and implementation guidance.

Architecture

Backend Structure

backend/
├── app/
│   ├── api/routes.py               # FastAPI endpoints
│   ├── core/database.py            # SQLite database operations  
│   ├── models/schemas.py           # Pydantic models
│   └── services/
│       ├── llm_service.py          # LLM provider integrations
│       ├── mcp_client.py           # Remote MCP protocol client
│       └── local_mcp_manager.py    # Local MCP process management
├── logs/                           # Application and MCP server logs
└── main.py                         # FastAPI application with lifespan management

Frontend Structure

frontend/
├── src/
│   ├── components/
│   │   ├── ui/                     # Shadcn/ui components
│   │   ├── ChatInterfaceSimple.tsx # Main chat interface with tool execution
│   │   └── SettingsPage.tsx        # Configuration management
│   ├── lib/
│   │   ├── api.ts                  # Backend API client
│   │   └── utils.ts                # Utility functions
│   ├── store/
│   │   └── useStore.ts             # Zustand state management
│   └── types/
│       └── api.ts                  # TypeScript interfaces
├── public/
│   └── robot-logo.png              # Application logo
└── AppMinimal.tsx                  # Main application component

Key Components

• ChatInterfaceSimple: Complete tool execution pipeline with UI
• ToolCallDisplay: Collapsible tool visualization component
• LocalMCPManager: Process management for local MCP servers
• LLMService: Multi-provider LLM integration with tool calling
• Database: SQLite storage for configurations and server state

API Endpoints

Core Endpoints

• GET / - API status
• POST /api/chat - Send message with tool execution support
• GET /api/llm/configs - List LLM configurations
• POST /api/llm/configs - Create LLM configuration
• POST /api/llm/configs/{id}/activate - Activate LLM configuration

MCP Management

• GET /api/mcp/servers - List all MCP servers
• GET /api/mcp/servers/{id} - Get server details with tools
• POST /api/mcp/servers - Create MCP server
• POST /api/mcp/servers/{id}/start - Start local MCP server
• POST /api/mcp/servers/{id}/stop - Stop local MCP server
• POST /api/mcp/call-tool - Execute MCP tool

Development

Running Development Servers

Recommended - Use the consolidated scripts:

# Start both servers
./start-dev.sh

# Stop both servers  
./stop-dev.sh

Development Status & Roadmap

The application is fully functional with recent improvements to error handling and OpenAI API compliance. For detailed development plans and improvement tasks, see the comprehensive roadmap in CLAUDE.md.

Recent Improvements (Completed):

• ✅ Fixed critical tool execution errors and OpenAI API compliance issues
• ✅ Added intelligent parameter correction for MCP validation errors
• ✅ Implemented robust retry mechanisms for failed tool calls
• ✅ Enhanced conversation history management for multi-turn interactions
• ✅ Added comprehensive error response handling for all tool call scenarios

Planned Improvements (organized by priority in CLAUDE.md):

• 🔄 Week 1 (Critical): Code quality fixes, error boundaries, performance logging
• 🔄 Week 2 (Architecture): Refactor large components, optimize re-renders, add caching
• 🔄 Week 3 (UX): User-friendly error messages, progress indicators, clean displays
• 🔄 Week 4 (Polish): Unit tests, security audit, TypeScript strict mode

For Contributors: See CLAUDE.md for detailed technical guidance, architecture documentation, and a comprehensive task list with specific file locations and implementation details.

Manual approach:

1. Backend Development:

``bash cd backend source venv/bin/activate # Windows: venv\Scripts\activate python main.py ``

1. Frontend Development:

``bash cd frontend npm run dev ``

Key Development Features

• Hot Reload: Both frontend and backend support hot reloading
• Logging: Comprehensive logging to logs/ directory
• Process Management: Automatic MCP server lifecycle management
• Error Handling: Graceful error handling with user feedback
• State Management: Persistent UI state with Zustand

Screenshots

• Chat Conversation with tool call

• Settings page for LLMs and MCP servers

Contributing

This is a demonstration project. Feel free to fork and extend it for your own needs.

License

Apache License 2.0

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: jeffvestal
• Source: jeffvestal/simple-mcp-client
• License: Apache-2.0

Install and usage instructions live in the source repository linked above.