odashun@ mcp % pwd
/Users/odashun/workspace/mcp

# チュートリアルに沿ってディレクトリ「weather」も作成します。
odashun@ mcp % mkdir weather
odashun@ mcp % cd weather

odashun@ weather % gradle init
Starting a Gradle Daemon (subsequent builds will be faster)

# 1:Applicationを指定
Select type of build to generate:
  1: Application
  2: Library
  3: Gradle plugin
  4: Basic (build structure only)
Enter selection (default: Application) [1..4] 1

# 今回はKotlinなので「2:Kotlin」を指定
Select implementation language:
  1: Java
  2: Kotlin
  3: Groovy
  4: Scala
  5: C++
  6: Swift
Enter selection (default: Java) [1..6] 2

# チュートリアルの記載に従い「17」を指定
Enter target Java version (min: 7, default: 21): 17

# プロジェクトの名前なので任意の文字列でOK
Project name (default: weather): weather

# お試しプロジェクトなので、「1:Single application project」を指定
Select application structure:
  1: Single application project
  2: Application and library project
Enter selection (default: Single application project) [1..2] 1

# お好みのDSLを指定する。今回は「1:Kotlin」を指定
Select build script DSL:
  1: Kotlin
  2: Groovy
Enter selection (default: Kotlin) [1..2] 1

# 今回テストケースを実装するわけではないので、なんでも良い。
Select test framework:
  1: kotlin.test
  2: JUnit Jupiter
Enter selection (default: kotlin.test) [1..2] 1

Generate build using new APIs and behavior (some features may change in the next minor release)? (default: no) [yes, no] yes


> Task :init
Learn more about Gradle by exploring our Samples at https://docs.gradle.org/8.13/samples/sample_building_kotlin_applications.html

BUILD SUCCESSFUL in 41s
1 actionable task: 1 executed

weather
├── app
│   ├── build.gradle.kts
│   └── src
│       ├── main
│       │   ├── kotlin
│       │   │   └── org
│       │   │       └── example
│       │   │           └── App.kt
│       │   └── resources
│       └── test
│           ├── kotlin
│           │   └── org
│           │       └── example
│           │           └── AppTest.kt
│           └── resources
├── gradle
│   ├── libs.versions.toml
│   └── wrapper
│       ├── gradle-wrapper.jar
│       └── gradle-wrapper.properties
├── gradle.properties
├── gradlew
├── gradlew.bat
└── settings.gradle.kts

val mcpVersion = "0.4.0"
val slf4jVersion = "2.0.9"
val ktorVersion = "3.1.1"

dependencies {
    implementation("io.modelcontextprotocol:kotlin-sdk:$mcpVersion")
    implementation("org.slf4j:slf4j-nop:$slf4jVersion")
    implementation("io.ktor:ktor-client-content-negotiation:$ktorVersion")
    implementation("io.ktor:ktor-serialization-kotlinx-json:$ktorVersion")
}

plugins {
    kotlin("plugin.serialization") version "1.9.0"
    id("com.github.johnrengelman.shadow") version "8.1.1"
}

    // Base URL for the Weather API
    val baseUrl = "https://api.weather.gov"

    // Create an HTTP client with a default request configuration and JSON content negotiation
    val httpClient = HttpClient {
        defaultRequest {
            url(baseUrl)
            headers {
                append("Accept", "application/geo+json")
                append("User-Agent", "WeatherApiClient/1.0")
            }
            contentType(ContentType.Application.Json)
        }
        // Install content negotiation plugin for JSON serialization/deserialization
        install(ContentNegotiation) {
            json(Json {
                ignoreUnknownKeys = true
                prettyPrint = true
            })
        }
    }

    val server = Server(
        Implementation( // MCPサーバの名前とバージョンを定義
            name = "weather",
            version = "1.0.0"
        ),
        ServerOptions( // MCPサーバの設定オプション
            // listChanged=trueにすることでツール内容に変更が入った際に通知処理を行う
                capabilities = ServerCapabilities(tools = ServerCapabilities.Tools(listChanged = true))
        )
    )

    server.addTool(
        name = "get_alerts", // ツール名
        description = """
            Get weather alerts for a US state. Input is Two-letter US state code (e.g. CA, NY)
        """.trimIndent(), // ツールの説明
        inputSchema = Tool.Input( // MCPクライアントから受け取る入力スキーマ（JSON）を定義する
            properties = buildJsonObject {
                putJsonObject("state") {
                    put("type", "string")
                    put("description", "Two-letter US state code (e.g. CA, NY)")
                }
            },
            required = listOf("state")
        )
    ) { request -> // ツールの実行処理を定義する
        val state = request.arguments["state"]?.jsonPrimitive?.content // リクエスト「state」パラメータを取得
        if (state == null) { // 「state」パラメータがnullの場合にエラーメッセージを返す
            return@addTool CallToolResult(
                content = listOf(TextContent("The 'state' parameter is required."))
            )
        }

        val alerts = httpClient.getAlerts(state) // APIから天気警報を取得

        CallToolResult(content = alerts.map { TextContent(it) }) // 取得した警報情報をMCPクライアントに返す
    }

    server.addTool(
        name = "get_forecast",
        description = """
            Get weather forecast for a specific latitude/longitude
        """.trimIndent(),
        inputSchema = Tool.Input(
            properties = buildJsonObject {
                putJsonObject("latitude") {
                    put("type", "number")
                }
                putJsonObject("longitude") {
                    put("type", "number")
                }
            },
            required = listOf("latitude", "longitude")
        )
    ) { request ->
        val latitude = request.arguments["latitude"]?.jsonPrimitive?.doubleOrNull
        val longitude = request.arguments["longitude"]?.jsonPrimitive?.doubleOrNull
        if (latitude == null || longitude == null) {
            return@addTool CallToolResult(
                content = listOf(TextContent("The 'latitude' and 'longitude' parameters are required."))
            )
        }

        val forecast = httpClient.getForecast(latitude, longitude)

        CallToolResult(content = forecast.map { TextContent(it) })
    }

    // Create a transport using standard IO for server communication
    val transport = StdioServerTransport(
        System.`in`.asInput(),
        System.out.asSink().buffered()
    )

    // 標準入出力を使用してMCPサーバーと通信するためのトランスポートを作成
    val transport = StdioServerTransport(
        System.`in`.asInput(),
        System.out.asSink().buffered()
    )

    // MCPサーバーを起動し、クライアント接続から終了まで待機するロジック
    runBlocking {
        server.connect(transport)    // ステップ4で作成したトランスポートのオブジェクトを用いてMCPクライアントとの双方向通信を開始
        val done = Job()             // サーバー終了検知用のJobオブジェクトを作成
        server.onClose {             // 接続が切断されたタイミングで、Jobを完了状態にする
            done.complete()
        }
        done.join()                  // Job完了（＝サーバー終了）までサスペンドして待機
    }

odashun@ weather % ./gradlew build
Reusing configuration cache.

[Incubating] Problems report is available at: file:///Users/odashun/workspace/mcp/weather/build/reports/problems/problems-report.html

Deprecated Gradle features were used in this build, making it incompatible with Gradle 9.0.

You can use '--warning-mode all' to show the individual deprecation warnings and determine if they come from your own scripts or plugins.

For more on this, please refer to https://docs.gradle.org/8.13/userguide/command_line_interface.html#sec:command_line_warnings in the Gradle documentation.

BUILD SUCCESSFUL in 2s
11 actionable tasks: 4 executed, 7 up-to-date
Configuration cache entry reused.

odashun@ weather % ls app/build/libs/app-all.jar
app/build/libs/app-all.jar

odashun@ weather % ls /Users/odashun/workspace/mcp/weather/app/build/libs/app-all.jar
/Users/odashun/workspace/mcp/weather/app/build/libs/app-all.jar

{
    "mcpServers": {
        "weather": {
            "command": "java",
            "args": [
                "-jar",
                "/Users/odashun/workspace/mcp/weather/app/build/libs/app-all.jar"
            ]
        }
    }
}

2025-04-21T03:22:30.169Z [weather] [info] Message from client: {"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"claude-ai","version":"0.1.0"}},"jsonrpc":"2.0","id":0}
エラー: メイン・クラスorg.example.AppKtを検出およびロードできませんでした
原因: java.lang.ClassNotFoundException: org.example.AppKt