Add Kotlin Weather STDIO server sample (#50)
* Add Kotlin Weather STDIO server sample * Update gradle build command in Readme to exclude tests
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Pavel Gorgulov
GitHub
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4 changed files with 863 additions and 0 deletions
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package io.modelcontextprotocol.sample.server
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import io.ktor.client.*
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import io.ktor.client.plugins.*
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import io.ktor.client.plugins.contentnegotiation.*
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import io.ktor.http.*
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import io.ktor.serialization.kotlinx.json.*
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import io.ktor.utils.io.streams.*
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import io.modelcontextprotocol.kotlin.sdk.*
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import io.modelcontextprotocol.kotlin.sdk.server.Server
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import io.modelcontextprotocol.kotlin.sdk.server.ServerOptions
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import io.modelcontextprotocol.kotlin.sdk.server.StdioServerTransport
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import kotlinx.coroutines.CompletableDeferred
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import kotlinx.coroutines.Job
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import kotlinx.coroutines.runBlocking
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import kotlinx.io.asSink
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import kotlinx.io.buffered
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import kotlinx.serialization.json.*
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// Main function to run the MCP server
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fun `run mcp server`() {
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val def = CompletableDeferred<Unit>()
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// Base URL for the Weather API
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val baseUrl = "https://api.weather.gov"
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// Create an HTTP client with a default request configuration and JSON content negotiation
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val httpClient = HttpClient {
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defaultRequest {
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url(baseUrl)
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headers {
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append("Accept", "application/geo+json")
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append("User-Agent", "WeatherApiClient/1.0")
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}
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contentType(ContentType.Application.Json)
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}
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// Install content negotiation plugin for JSON serialization/deserialization
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install(ContentNegotiation) {
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json(Json {
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ignoreUnknownKeys = true
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prettyPrint = true
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})
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}
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}
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// Create the MCP Server instance with a basic implementation
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val server = Server(
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Implementation(
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name = "weather", // Tool name is "weather"
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version = "1.0.0" // Version of the implementation
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),
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ServerOptions(
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capabilities = ServerCapabilities(tools = ServerCapabilities.Tools(listChanged = true))
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)
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) { def.complete(Unit) }
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// Register a tool to fetch weather alerts by state
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server.addTool(
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name = "get_alerts",
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description = """
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Get weather alerts for a US state. Input is Two-letter US state code (e.g. CA, NY)
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""".trimIndent(),
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inputSchema = Tool.Input(
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properties = JsonObject(
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mapOf(
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"state" to JsonObject(
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mapOf(
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"type" to JsonPrimitive("string"),
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"description" to JsonPrimitive("Two-letter US state code (e.g. CA, NY)")
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)
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),
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)
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),
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required = listOf("state")
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)
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) { request ->
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val state = request.arguments["state"]?.jsonPrimitive?.content
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if (state == null) {
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return@addTool CallToolResult(
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content = listOf(TextContent("The 'state' parameter is required."))
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)
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}
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val alerts = httpClient.getAlerts(state)
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CallToolResult(content = alerts.map { TextContent(it) })
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}
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// Register a tool to fetch weather forecast by latitude and longitude
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server.addTool(
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name = "get_forecast",
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description = """
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Get weather forecast for a specific latitude/longitude
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""".trimIndent(),
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inputSchema = Tool.Input(
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properties = JsonObject(
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mapOf(
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"latitude" to JsonObject(mapOf("type" to JsonPrimitive("number"))),
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"longitude" to JsonObject(mapOf("type" to JsonPrimitive("number"))),
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)
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),
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required = listOf("latitude", "longitude")
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)
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) { request ->
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val latitude = request.arguments["latitude"]?.jsonPrimitive?.doubleOrNull
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val longitude = request.arguments["longitude"]?.jsonPrimitive?.doubleOrNull
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if (latitude == null || longitude == null) {
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return@addTool CallToolResult(
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content = listOf(TextContent("The 'latitude' and 'longitude' parameters are required."))
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)
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}
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val forecast = httpClient.getForecast(latitude, longitude)
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CallToolResult(content = forecast.map { TextContent(it) })
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}
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// Create a transport using standard IO for server communication
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val transport = StdioServerTransport(
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System.`in`.asInput(),
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System.out.asSink().buffered()
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)
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runBlocking {
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server.connect(transport)
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val done = Job()
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server.onCloseCallback = {
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done.complete()
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}
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done.join()
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}
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}
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package io.modelcontextprotocol.sample.server
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import io.ktor.client.HttpClient
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import io.ktor.client.call.body
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import io.ktor.client.request.get
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import kotlinx.serialization.Serializable
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import kotlinx.serialization.json.JsonObject
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// Extension function to fetch forecast information for given latitude and longitude
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suspend fun HttpClient.getForecast(latitude: Double, longitude: Double): List<String> {
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// Build the URI using provided latitude and longitude
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val uri = "/points/$latitude,$longitude"
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// Request the points data from the API
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val points = this.get(uri).body<Points>()
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// Request the forecast using the URL provided in the points response
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val forecast = this.get(points.properties.forecast).body<Forecast>()
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// Map each forecast period to a formatted string
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return forecast.properties.periods.map { period ->
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"""
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${period.name}:
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Temperature: ${period.temperature} ${period.temperatureUnit}
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Wind: ${period.windSpeed} ${period.windDirection}
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Forecast: ${period.detailedForecast}
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""".trimIndent()
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}
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}
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// Extension function to fetch weather alerts for a given state
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suspend fun HttpClient.getAlerts(state: String): List<String> {
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// Build the URI using the given state code
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val uri = "/alerts/active/area/$state"
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// Request the alerts data from the API
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val alerts = this.get(uri).body<Alert>()
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// Map each alert feature to a formatted string
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return alerts.features.map { feature ->
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"""
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Event: ${feature.properties.event}
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Area: ${feature.properties.areaDesc}
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Severity: ${feature.properties.severity}
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Description: ${feature.properties.description}
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Instruction: ${feature.properties.instruction}
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""".trimIndent()
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}
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}
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// Data class representing the points response from the API
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@Serializable
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data class Points(
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val properties: Properties
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) {
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@Serializable
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data class Properties(val forecast: String)
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}
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// Data class representing the forecast response from the API
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@Serializable
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data class Forecast(
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val properties: Properties
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) {
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@Serializable
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data class Properties(val periods: List<Period>)
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@Serializable
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data class Period(
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val number: Int, val name: String, val startTime: String, val endTime: String,
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val isDaytime: Boolean, val temperature: Int, val temperatureUnit: String,
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val temperatureTrend: String, val probabilityOfPrecipitation: JsonObject,
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val windSpeed: String, val windDirection: String,
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val shortForecast: String, val detailedForecast: String,
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)
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}
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// Data class representing the alerts response from the API
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@Serializable
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data class Alert(
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val features: List<Feature>
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) {
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@Serializable
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data class Feature(
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val properties: Properties
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)
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@Serializable
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data class Properties(
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val event: String, val areaDesc: String, val severity: String,
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val description: String, val instruction: String?,
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)
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}
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@ -0,0 +1,3 @@
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package io.modelcontextprotocol.sample.server
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fun main() = `run mcp server`()
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@ -0,0 +1,56 @@
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package io.modelcontextprotocol.sample.client
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import io.modelcontextprotocol.kotlin.sdk.CallToolRequest
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import io.modelcontextprotocol.kotlin.sdk.Implementation
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import io.modelcontextprotocol.kotlin.sdk.TextContent
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import io.modelcontextprotocol.kotlin.sdk.client.Client
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import io.modelcontextprotocol.kotlin.sdk.client.StdioClientTransport
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import kotlinx.coroutines.runBlocking
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import kotlinx.io.asSink
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import kotlinx.io.asSource
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import kotlinx.io.buffered
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import kotlinx.serialization.json.JsonObject
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import kotlinx.serialization.json.JsonPrimitive
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fun main(): Unit = runBlocking {
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val process = ProcessBuilder("java", "-jar", "build/libs/weather-stdio-server-0.1.0-all.jar")
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.start()
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val transport = StdioClientTransport(
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input = process.inputStream.asSource().buffered(),
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output = process.outputStream.asSink().buffered()
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)
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// Initialize the MCP client with client information
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val client = Client(
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clientInfo = Implementation(name = "weather", version = "1.0.0"),
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)
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client.connect(transport)
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val toolsList = client.listTools()?.tools?.map { it.name }
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println("Available Tools = $toolsList")
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val weatherForecastResult = client.callTool(
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CallToolRequest(
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name = "get_forecast",
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arguments = JsonObject(mapOf("latitude" to JsonPrimitive(38.5816), "longitude" to JsonPrimitive(-121.4944)))
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)
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)?.content?.map { if (it is TextContent) it.text else it.toString() }
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println("Weather Forcast: ${weatherForecastResult?.joinToString(separator = "\n", prefix = "\n", postfix = "\n")}")
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val alertResult =
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client.callTool(
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CallToolRequest(
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name = "get_alerts",
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arguments = JsonObject(mapOf("state" to JsonPrimitive("TX")))
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)
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)?.content?.map { if (it is TextContent) it.text else it.toString() }
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println("Alert Response = $alertResult")
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client.close()
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}
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