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What is Nexus?

Nexus is a Model Context Protocol (MCP) server that provides AI-powered web search functionality through the OpenRouter API. It integrates with MCP-compatible clients including Claude Desktop and Cursor, providing search capabilities via the Perplexity Sonar model family.

Key Characteristics

• Zero-install deployment: Executable via npx with no build requirements
• OpenRouter integration: Uses Perplexity Sonar models for web search with citations
• MCP protocol compliance: Implements standard MCP tool and resource interfaces
• Production architecture: Includes request caching, deduplication, retry logic, and error handling
• Type-safe implementation: Full TypeScript coverage with strict type checking

Features

Deployment

• NPX-based execution with zero local installation
• Cross-platform compatibility (macOS, Linux, Windows)
• Node.js 18+ runtime requirement
• Automated version updates via npm registry

Search Capabilities

• Perplexity Sonar model family integration
• Real-time web search with current information
• Structured citation extraction from responses
• Configurable model parameters (temperature, max tokens, penalties)

Architecture

• Comprehensive error handling with typed error classes
• Request caching with configurable TTL
• Request deduplication for concurrent identical queries
• Automatic retry logic with exponential backoff
• Winston-based structured logging
• TypeScript strict mode implementation with full type coverage

Quick Start

Prerequisites

• Node.js 18 or higher
• OpenRouter API key (register at openrouter.ai)

NPX Installation

Execute the server without local installation:

# Set your OpenRouter API key
export OPENROUTER_API_KEY=your-api-key-here

# Run the server via NPX
npx nexus-mcp

The server starts and listens for MCP client connections via STDIO transport.

Testing the NPX Installation

# Test the CLI help
npx nexus-mcp --help

# Test the version
npx nexus-mcp --version

# Run with your API key
OPENROUTER_API_KEY=your-key npx nexus-mcp

Alternative: Local Development Installation

For local development or customization:

1. Clone the repository:

git clone https://github.com/adawalli/nexus.git
cd nexus

2. Install dependencies:

npm install

3. Build the server:

npm run build

4. Configure your OpenRouter API key:

# Copy the example environment file
cp .env.example .env

# Edit .env and add your actual API key
# OPENROUTER_API_KEY=your-api-key-here

5. Test the server:

npm start

Integration with MCP Clients

NPX-Based Integration (Recommended)

Configure MCP clients to execute the server via NPX:

Claude Code

Configuration in ~/.claude/mcp_settings.json:

{
  "mcpServers": {
    "nexus": {
      "command": "npx",
      "args": ["nexus-mcp"],
      "env": {
        "OPENROUTER_API_KEY": "your-api-key-here"
      }
    }
  }
}

Restart Claude Code after configuration changes.

Cursor

Add server configuration in Cursor's MCP settings:

• Name: nexus
• Command: npx
• Args: ["nexus-mcp"]
• Environment Variables: OPENROUTER_API_KEY=your-api-key-here

Restart Cursor after configuration changes.

Generic MCP Client Configuration

Standard MCP client connection parameters:

• Transport: stdio
• Command: npx
• Args: ["nexus-mcp"]
• Environment: OPENROUTER_API_KEY=your-api-key-here

Alternative: Local Installation

If you prefer using a local installation (after following the local development setup):

{
  "mcpServers": {
    "nexus": {
      "command": "node",
      "args": ["/path/to/nexus-mcp/dist/cli.js"],
      "env": {
        "OPENROUTER_API_KEY": "your-api-key-here"
      }
    }
  }
}

Usage

Once integrated, you can use the search tool in your MCP client:

Basic Search

Use the search tool to find information about "latest developments in AI"

Advanced Search with Parameters

Search for "climate change solutions" using:
- Model: perplexity/sonar
- Max tokens: 2000
- Temperature: 0.3

Available Tools

search

The main search tool that provides AI-powered web search capabilities.

Parameters:

• query (required): Search query (1-2000 characters)
• model (optional): Perplexity model to use (default: "perplexity/sonar")
• maxTokens (optional): Maximum response tokens (1-4000, default: 1000)
• temperature (optional): Response randomness (0-2, default: 0.7)

Example Response:

Based on current information, here are the latest developments in AI...

[Detailed AI-generated response with current information]

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**Search Metadata:**
- Model: perplexity/sonar
- Response time: 1250ms
- Tokens used: 850
- Sources: 5 found

Configuration

Environment Variables

• OPENROUTER_API_KEY (required): Your OpenRouter API key
• NODE_ENV (optional): Environment setting (development, production, test)
• LOG_LEVEL (optional): Logging level (debug, info, warn, error)

Advanced Configuration

The server supports additional configuration through environment variables:

• OPENROUTER_TIMEOUT_MS: Request timeout in milliseconds (default: 30000)
• OPENROUTER_MAX_RETRIES: Maximum retry attempts (default: 3)
• OPENROUTER_BASE_URL: Custom OpenRouter API base URL

Resources

The server provides a configuration status resource at config://status that shows:

• Server health status
• Configuration information (with masked API key)
• Search tool availability
• Server uptime and version

Troubleshooting

NPX-Specific Issues

"npx: command not found"

• Ensure Node.js 18+ is installed: node --version
• Update npm: npm install -g npm@latest

"Cannot find package 'nexus-mcp'"

• The package may not be published yet. Use local installation instead
• Verify network connectivity for npm registry access

NPX takes a long time to start

• This is normal on first run as NPX downloads the package
• Subsequent runs will be faster due to caching
• For faster startup, use local installation instead

"Permission denied" errors with NPX

• Try: npx --yes nexus-mcp --stdio
• Or set npm permissions: npm config set user 0 && npm config set unsafe-perm true

Common Issues

"Search functionality is not available"

• Ensure OPENROUTER_API_KEY environment variable is set
• Verify your API key is valid at OpenRouter
• Check the server logs for initialization errors

"Authentication failed: Invalid API key"

• Double-check your API key format and validity
• Ensure the key has sufficient credits/permissions
• Test the key directly at OpenRouter dashboard

"Rate limit exceeded"

• Wait for the rate limit to reset (usually 1 minute)
• Consider upgrading your OpenRouter plan for higher limits
• Monitor usage in your OpenRouter dashboard

Connection timeouts

• Check your internet connection
• The server will automatically retry failed requests
• Increase timeout if needed: OPENROUTER_TIMEOUT_MS=60000

MCP client can't connect to server

• Verify your MCP configuration uses the correct command and arguments
• Check that Node.js 18+ is available in your MCP client's environment
• Ensure the API key is properly set in the environment variables

Debug Logging

Enable debug logging by:

For local development: Add LOG_LEVEL=debug to your .env file

For MCP clients: Add LOG_LEVEL: "debug" to the env section of your MCP configuration

This will provide detailed information about:

• Configuration loading
• API requests and responses
• Error details and stack traces
• Performance metrics

Testing Connection

You can test if the server is working by checking the configuration status resource in your MCP client, or by running a simple search query.

Development

For developers working on this server:

# Development with hot reload
npm run dev

# Run tests
npm test

# Run tests with coverage
npm run test:coverage

# Lint code
npm run lint

# Format code
npm run format

API Costs

OpenRouter charges for API usage based on token consumption:

• Pricing: See current rates at OpenRouter Models
• Monitoring: Usage tracking available in OpenRouter dashboard
• Limits: Configure spending limits in OpenRouter account settings
• Optimization: Server implements response caching and request deduplication to minimize redundant API calls

📚 Documentation

🤝 Contributing

We welcome contributions from developers of all experience levels!

🌟 Recognition

Contributors are recognized in our:

• Contributors list
• Release notes for significant contributions
• Community spotlights and testimonials

🔗 Related Projects

• Model Context Protocol - The standard we implement
• OpenRouter - Our AI model provider
• Claude Desktop - Primary MCP client
• Cursor - AI-powered code editor with MCP support

📞 Support & Community

📄 License

MIT License - see LICENSE file for details.

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