Transport Overview

Transports handle the communication between MCP clients and your server. scala-mcp-sdk provides two transport options.

Available Transports

Transport	Use Case	Client Examples
Stdio	CLI tools, local processes	Claude Desktop, VS Code extensions
Streamable HTTP	Web services, remote access	Web apps, multi-client scenarios

Choosing a Transport

Use Stdio When

• Building a CLI tool or local integration
• The client spawns your server as a subprocess
• You want the simplest deployment (single binary)
• Single client per server instance

Use Streamable HTTP When

• Deploying as a web service
• Multiple clients need to connect
• You need bidirectional streaming
• Integration with existing HTTP infrastructure

Transport Architecture

Both transports implement the same Transport[F] trait:

trait Transport[F[_]] {
  def run(handler: RequestHandler[F]): Resource[F, Unit]
}

This means your McpServer works identically with either transport. You only change the transport layer, not your business logic.

Feature Differences

Feature	Stdio	Streamable HTTP
Multi-client	No (1 client per process)	Yes
Bidirectional streaming	N/A	Yes
Session management	Implicit	Explicit
Resource subscriptions	Limited	Full support
Deployment	Binary/script	HTTP server

Next Steps

• Stdio Transport - For CLI and desktop integrations
• Streamable HTTP Transport - For web services