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

modelcontextprotocol.github.io/kotlin-sdk/

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MIT license

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.github		.github
buildSrc		buildSrc
docs		docs
gradle		gradle
kotlin-sdk-client		kotlin-sdk-client
kotlin-sdk-core		kotlin-sdk-core
kotlin-sdk-server		kotlin-sdk-server
kotlin-sdk-test		kotlin-sdk-test
kotlin-sdk		kotlin-sdk
samples		samples
.editorconfig		.editorconfig
.gitignore		.gitignore
AGENTS.md		AGENTS.md
CODE_OF_CONDUCT.md		CODE_OF_CONDUCT.md
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
README.md		README.md
build.gradle.kts		build.gradle.kts
gradle.properties		gradle.properties
gradlew		gradlew
gradlew.bat		gradlew.bat
settings.gradle.kts		settings.gradle.kts

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

MCP SDK usesKtor, but does not come with a specific engine dependency.You should addKtor clientand/orKtor server dependencyto your project yourself, e.g.:

dependencies {// for client:    implementation("io.ktor:ktor-client-cio:$ktorVersion")// for server:    implementation("io.ktor:ktor-server-netty:$ktorVersion")    }

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            )        )    )){"This server provides example resources and demonstrates MCP capabilities." }// 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)                )            ),        ) {"This SSE server provides prompts and resources via Server-Sent Events."        }    }}

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)                        )                    ),                ) {"Connect via SSE to interact with this MCP server."                }            }        }    }}