kotlin-sdk/samples/simple-streamable-server

Simple Streamable HTTP Server

A minimal MCP server using the recommended Streamable HTTP transport with optional Bearer token authentication.

Overview

This sample demonstrates a Streamable HTTP MCP server built with Ktor. It exposes tools, a prompt template, and a resource over HTTP, and optionally supports Bearer token authentication. The multi-greet tool showcases server-to-client logging notifications with streaming delays.

Prerequisites

• JDK 17+

Build & Run

Without authentication

./gradlew run

The server starts on http://localhost:3001/mcp by default.

Connect with the MCP Inspector:

npx @modelcontextprotocol/inspector

In the Inspector UI, select Streamable HTTP transport and enter http://localhost:3001/mcp.

Pass a port number as an argument to change it:

./gradlew run --args="8080"

With authentication

MCP_AUTH_TOKEN=my-secret ./gradlew run --args="--auth"

When --auth is passed, clients must include an Authorization: Bearer <token> header. The token is read from the MCP_AUTH_TOKEN environment variable (required when --auth is used).

Authentication caveats

This sample is intended for demonstration only. In production you should:

• Use a proper identity provider instead of a static token.
• Restrict CORS origins to your deployment domain — the sample allows all origins.
• Serve the endpoint over HTTPS.

MCP Capabilities

Tools

Name	Description
greet	Returns a greeting for a given name.
multi-greet	Sends logging notifications between delayed greetings, demonstrating streaming.

Prompts

Name	Description
greeting-template	Generates a friendly greeting message for a given name.

Resources

Name	URI	Description
Default Greeting	https://example.com/greetings/default	Returns a static "Hello, world!" text.