kotlin-sdk/samples/kotlin-mcp-server

Kotlin MCP Server

A sample MCP server demonstrating multiple transport modes: STDIO, SSE (plain), and SSE (Ktor plugin).

Note: The SSE transport modes are provided for backward compatibility. For new projects, consider using the simple-streamable-server sample, which uses the recommended Streamable HTTP transport.

Overview

This sample registers a prompt, a tool, and a resource, then lets you choose how to expose them. STDIO mode is the default and is best for process-based clients. The two SSE modes show how to serve MCP over HTTP using either a manual Ktor routing setup or the built-in mcp { } Ktor plugin.

Prerequisites

• JDK 17+
• MCP Inspector (optional, for testing)

Build & Run

STDIO mode (default)

./gradlew run

Or explicitly:

./gradlew run --args="--stdio"

Connect with the MCP Inspector:

npx @modelcontextprotocol/inspector --config samples/kotlin-mcp-server/mcp-inspector-config.json --server stdio-server

SSE with Ktor plugin

./gradlew run --args="--sse-server-ktor 3002"

Connect with the MCP Inspector:

npx @modelcontextprotocol/inspector --config samples/kotlin-mcp-server/mcp-inspector-config.json --server sse-ktor-server

SSE with plain configuration

Known issue: This mode may not work correctly at this time.

./gradlew run --args="--sse-server 3001"

Connect with the MCP Inspector:

npx @modelcontextprotocol/inspector --config samples/kotlin-mcp-server/mcp-inspector-config.json --server sse-server

MCP Capabilities

Tools

Name	Description
kotlin-sdk-tool	A test tool that returns a "Hello, world!" greeting.

Prompts

Name	Description
Kotlin Developer	Generates a prompt to develop a small Kotlin application for a given project name.

Resources

Name	URI	Description
Web Search	https://search.com/	A placeholder resource demonstrating resource handling.