SearXNG MCP Bridge Server

This is a Model Context Protocol (MCP) server that acts as a bridge to a SearXNG instance. It allows compatible clients to perform searches using a configured SearXNG instance via MCP tools.

Requirements

• Node.js 25.x
• npm 11.x or newer

Quick Start (Using from npm)

1. Set up a SearXNG instance:

   # Using Docker
   docker run -d -p 8888:8080 --name searxng searxng/searxng

2. Install and run the MCP bridge

   Default (STDIO, unchanged):

   # Run directly with npx (default - stdio transport)
   npx -y @nitish-raj/searxng-mcp-bridge

   Optional: Run as an HTTP server (new, opt-in)

    # Using env variables (recommended)
     TRANSPORT=http PORT=3002 HOST=127.0.0.1 SEARXNG_INSTANCE_URL=http://localhost:8080 npx -y @nitish-raj/searxng-mcp-bridge
   
   
   
   # Or run the built bundle
   TRANSPORT=http node build/index.js

3. Configure in your MCP settings file (stdio / legacy clients) Add to your MCP settings file (e.g., ~/.vscode-server/.../mcp_settings.json):

   {
     "mcpServers": {
       "searxng-bridge": {
         "command": "npx",
         "args": [
          "-y",
          "@nitish-raj/searxng-mcp-bridge"
          ],
          "env": {
            "SEARXNG_INSTANCE_URL": "http://localhost:8080"
          },
         "disabled": false
       }
     }
   }

HTTP Configuration: Set TRANSPORT=http to run the bridge over HTTP instead of stdio. The transport mode can be configured via environment variables.

Features

• Search Tool: Perform web searches using SearXNG with configurable parameters
• Health Check: Monitor SearXNG instance connectivity and performance
• Dual Transport: Supports both STDIO (default) and HTTP transports
• Session Management: HTTP transport includes session-based connections
• CORS Support: Proper cross-origin headers for web client integration
• Rate Limiting: Built-in protection against excessive requests (HTTP mode)

Configuration

• SEARXNG_INSTANCE_URL — REQUIRED. The full URL of the SearXNG instance (e.g., http://localhost:8080).
• TRANSPORT — Transport protocol: stdio (default) or http
• PORT — HTTP server port. Default: 3000 (use 3002 for development)
• HOST — Server bind address. Default: 127.0.0.1 (use 0.0.0.0 for containers)
• CORS_ORIGIN — Comma-separated list of allowed origins for CORS. Default: localhost:3002 (development) or * (production)
• MCP_HTTP_BEARER — Optional bearer token for HTTP authentication HTTP Transport Features:
• Session management with mcp-session-id headers
• Secure CORS with origin whitelist validation
• Rate limiting (100 requests/minute per IP)
• Optional bearer authentication via MCP_HTTP_BEARER
• DNS rebinding protection

Security Notes:

• CORS uses secure whitelist in development (localhost:3002 only)
• Production reflects specific origins for credentialed requests (CORS-compliant)
• Set CORS_ORIGIN to customize allowed origins for your use case
• Set TRANSPORT=stdio to revert to stdio mode

HTTP Transport

The HTTP transport implements the MCP Streamable HTTP specification (2025-03-26) with the following endpoints:

MCP Endpoints:

• POST /mcp - Send MCP requests
• GET /mcp - Server-Sent Events for notifications
• DELETE /mcp - Terminate sessions
• OPTIONS /mcp - CORS preflight requests

System Endpoints:

• GET /healthz - Health check and status

Test HTTP endpoint:

curl -X POST http://localhost:3002/mcp \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}'

This returns a JSON-RPC response with the list of available tools (search and health_check).

Docker

The Dockerfile exposes port 8081 for HTTP transport. To run the container and allow HTTP access:

# Build (example)
docker build -t searxng-mcp-bridge .

# Run mapping port 8081
 docker run -d -p 8081:8081 --env SEARXNG_INSTANCE_URL=http://localhost:8080 --name searxng-mcp-bridge searxng-mcp-bridge

# To run HTTP transport inside container:
 docker run -d -p 8081:8081 -e TRANSPORT=http -e PORT=8081 -e SEARXNG_INSTANCE_URL=http://localhost:8080 searxng-mcp-bridge

Note: when containerized set HOST=0.0.0.0 or rely on the default exposed port mapping.

Usage

STDIO Clients: Use the tool unchanged - no configuration changes required.

HTTP Clients: Connect to http://localhost:3002/mcp (development port) and send MCP JSON-RPC requests.

Development

• npm install: Install dependencies.
• npm run build: Compile TypeScript to JavaScript.
• npm run watch: Watch for changes and rebuild automatically.
• npm run inspector: Run the MCP inspector to test the server.
• npm run start:http: Start server in HTTP streaming mode on localhost:3002.

Migration & Compatibility

Backward Compatibility:

• STDIO remains the default transport - existing users need no changes
• All tool names, parameters, and responses remain unchanged
• Configuration is opt-in via environment variables

Migration to HTTP:

• Set TRANSPORT=http to enable HTTP transport
• Configure PORT and HOST as needed
• Update client to use HTTP endpoint instead of stdio

Rollback:

• Set TRANSPORT=stdio or omit the variable to return to stdio