Transport Modes

MCP servers can communicate with clients through different transport mechanisms. Each transport is optimized for specific use cases and client types.

stdio Transport

The stdio (standard input/output) transport is used for direct client connections.

Characteristics

• Communicates via standard input/output streams
• Logs go to stderr to avoid interfering with protocol messages
• Ideal for desktop applications and command-line tools
• Used by Claude Desktop and similar clients

Usage

Recommended: Using Arcade CLI

# Run with stdio transport
uv run server.py stdio

Alternative: Direct Python

# Run your server directly
uv run server.py stdio

# Or with python
app.run(transport="stdio")

Client Configuration

For Claude Desktop, use the arcade configure command:

arcade configure claude --from-local

Or manually edit ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "my-tools": {
      "command": "arcade",
      "args": ["mcp", "stdio"],
      "cwd": "/path/to/your/tools"
    }
  }
}

HTTP Transport

The HTTP transport provides REST/SSE endpoints for web-based clients.

Characteristics

• RESTful API with Server-Sent Events (SSE) for streaming
• Supports hot reload for development
• Includes health checks and API documentation
• Can be deployed behind reverse proxies
• Suitable for web applications and services

Usage

Recommended: Using Arcade CLI

# Run with HTTP transport (default)
uv run server.py
uv run server.py http

Alternative: Direct Python

# Run your server directly
uv run server.py

# Or with python
app.run(transport="http", host="0.0.0.0", port=8080)

Endpoints

When running in HTTP mode, the server provides:

• GET /health - Health check endpoint
• GET /mcp - SSE endpoint for MCP protocol
• GET /docs - Swagger UI documentation (debug mode)
• GET /redoc - ReDoc documentation (debug mode)

Development Features

With Arcade CLI:

# Enable hot reload and debug mode
app.run(host="127.0.0.1", port=8000, reload=True)

# This enables:
# - Automatic restart on code changes
# - Detailed error messages
# - API documentation endpoints
# - Verbose logging

Choosing a Transport

Use stdio when:

• Integrating with desktop applications (Claude Desktop, VS Code)
• Building command-line tools
• You need simple, direct communication
• Running in environments without network access

Use HTTP when:

• Building web applications
• Deploying to cloud environments
• You need to support multiple concurrent clients
• Integrating with existing web services
• You want API documentation and testing tools

Transport Configuration

Environment Variables

Both transports respect common environment variables:

# Server identification
MCP_SERVER_NAME="My MCP Server"
MCP_SERVER_VERSION="1.0.0"

# Logging
MCP_DEBUG=true
MCP_LOG_LEVEL=DEBUG

# HTTP-specific
MCP_HTTP_HOST=0.0.0.0
MCP_HTTP_PORT=8080

Programmatic Configuration

When using MCPApp:

from arcade_mcp_server import MCPApp

app = MCPApp(
    name="my-server",
    version="1.0.0",
    log_level="DEBUG"
)

# Run with specific transport
if __name__ == "__main__":
    import sys

    if len(sys.argv) > 1 and sys.argv[1] == "stdio":
        app.run(transport="stdio")
    else:
        app.run(transport="http", host="0.0.0.0", port=8080)

Security Considerations

stdio Transport

• Inherits security context of the parent process
• No network exposure
• Suitable for trusted environments

HTTP Transport

• Exposes network endpoints
• Should use authentication in production
• Consider using HTTPS with reverse proxy
• Implement rate limiting for public deployments

Advanced Transport Features

Custom Middleware (HTTP)

Add custom middleware to HTTP transports:

from arcade_mcp_server import MCPApp

app = MCPApp(name="my-server")

# Add custom middleware
@app.middleware("http")
async def add_custom_headers(request, call_next):
    response = await call_next(request)
    response.headers["X-Custom-Header"] = "value"
    return response

Transport Events

Listen to transport lifecycle events:

@app.on_event("startup")
async def startup_handler():
    print("Server starting up...")

@app.on_event("shutdown")
async def shutdown_handler():
    print("Server shutting down...")