Transport Modes

Understanding MCP transport protocols and when to use each

The Sei MCP Server supports three transport modes for different integration scenarios. In most cases, stdio is the best choice, but understanding these modes is important if you need a remote MCP server or if your AI tool doesn’t support MCP. Each transport offers unique advantages depending on your use case and client requirements.

Transport Overview

stdio

Default Mode Direct process communication via standard input/output streams.

streamable-http

HTTP API RESTful HTTP server with streaming capabilities for web integrations.

http-sse (deprecated)

Server-Sent Events HTTP with server-sent events (deprecated, use streamable-http instead).

Choosing the Right Transport

stdio - Best for Cursor, Windsurf, & local clients

Recommended for:

• Claude Desktop, Cursor, Windsurf integrations
• Local development and testing
• Maximum performance requirements

Pros:

• Fastest performance (no network overhead)
• Automatic lifecycle management
• Native MCP client support

Cons:

• Limited to local process communication
• No remote access capabilities

Security:

• Process isolation (server runs as child process)
• No network exposure (communication via local IPC)
• Client-managed lifecycle

streamable-http - Best for remote access or tools that don't support MCP

Recommended for:

• Remote server deployments
• Custom HTTP clients
• Tools that don’t support MCP
• Web applications

Pros:

• Network accessible
• Standard HTTP protocols
• Scalable and load-balanceable
• Works with any HTTP client

Cons:

• Network latency overhead
• Requires manual server management
• Additional security considerations

Security:

• Network exposure (server accessible over HTTP)
• Consider implementing API keys or tokens
• Configure CORS policies as needed
• Restrict access to trusted networks
• Use reverse proxy with HTTPS for production

http-sse - Deprecated, use streamable-http instead

Status: Deprecated - migrate to streamable-http

This transport is no longer recommended for new implementations. Existing users should migrate to streamable-http for better performance and standards compliance.

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Configuration

stdio

Claude Desktop

{
  "mcpServers": {
    "sei": {
      "command": "npx",
      "args": ["-y", "@sei-js/mcp-server"]
    }
  }
}

Environment Variables

# stdio is the default, no configuration needed
SERVER_TRANSPORT=stdio  # Optional, this is default
npx @sei-js/mcp-server

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