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The official Kotlin SDK for Model Context Protocol servers and clients. Maintained in collaboration with JetBrains

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MIT license

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MCP Kotlin SDK

Kotlin Multiplatform implementation of theModel Context Protocol (MCP),providing both client and server capabilities for integrating with LLM surfaces across various platforms.

Overview

The Model Context Protocol allows applications to provide context for LLMs in a standardized way,separating the concerns of providing context from the actual LLM interaction.This SDK implements the MCP specification for Kotlin,enabling you to build applications that can communicate using MCP on the JVM, WebAssembly and iOS.

Build MCP clients that can connect to any MCP server
Create MCP servers that expose resources, prompts and tools
Use standard transports like stdio, SSE, and WebSocket
Handle all MCP protocol messages and lifecycle events

Samples

kotlin-mcp-server: demonstrates a multiplatform (JVM, Wasm) MCP server setup with various features and transports.
weather-stdio-server: shows how to build a Kotlin MCP server providing weather forecast and alerts using STDIO transport.
kotlin-mcp-client: demonstrates building an interactive Kotlin MCP client that connects to an MCP server via STDIO and integrates with Anthropic’s API.

Installation

Add the new repository to your build file:

repositories {    mavenCentral()}

Add the dependency:

dependencies {// Use the badge above for the latest version    implementation("io.modelcontextprotocol:kotlin-sdk:$mcpVersion")}

Quick Start

Creating a Client

importio.modelcontextprotocol.kotlin.sdk.client.Clientimportio.modelcontextprotocol.kotlin.sdk.client.StdioClientTransportimportio.modelcontextprotocol.kotlin.sdk.Implementationval client=Client(    clientInfo=Implementation(        name="example-client",        version="1.0.0"    ))val transport=StdioClientTransport(    inputStream= processInputStream,    outputStream= processOutputStream)// Connect to serverclient.connect(transport)// List available resourcesval resources= client.listResources()// Read a specific resourceval resourceContent= client.readResource(ReadResourceRequest(uri="file:///example.txt"))

Creating a Server

importio.modelcontextprotocol.kotlin.sdk.server.Serverimportio.modelcontextprotocol.kotlin.sdk.server.ServerOptionsimportio.modelcontextprotocol.kotlin.sdk.server.StdioServerTransportimportio.modelcontextprotocol.kotlin.sdk.ServerCapabilitiesval server=Server(    serverInfo=Implementation(        name="example-server",        version="1.0.0"    ),    options=ServerOptions(        capabilities=ServerCapabilities(            resources=ServerCapabilities.Resources(                subscribe=true,                listChanged=true            )        )    ))// Add a resourceserver.addResource(    uri="file:///example.txt",    name="Example Resource",    description="An example text file",    mimeType="text/plain") { request->ReadResourceResult(        contents=listOf(TextResourceContents(                text="This is the content of the example resource.",                uri= request.uri,                mimeType="text/plain"            )        )    )}// Start server with stdio transportval transport=StdioServerTransport()server.connect(transport)

Using SSE Transport

Directly in Ktor'sApplication:

importio.ktor.server.application.*importio.modelcontextprotocol.kotlin.sdk.server.mcpfun Application.module() {    mcp {Server(            serverInfo=Implementation(                name="example-sse-server",                version="1.0.0"            ),            options=ServerOptions(                capabilities=ServerCapabilities(                    prompts=ServerCapabilities.Prompts(listChanged=null),                    resources=ServerCapabilities.Resources(subscribe=null, listChanged=null)                )            )        )    }}

Inside a custom Ktor'sRoute:

importio.ktor.server.application.*importio.ktor.server.sse.SSEimportio.modelcontextprotocol.kotlin.sdk.server.mcpfun Application.module() {    install(SSE)    routing {        route("myRoute") {            mcp {Server(                    serverInfo=Implementation(                        name="example-sse-server",                        version="1.0.0"                    ),                    options=ServerOptions(                        capabilities=ServerCapabilities(                            prompts=ServerCapabilities.Prompts(listChanged=null),                            resources=ServerCapabilities.Resources(subscribe=null, listChanged=null)                        )                    )                )            }        }    }}