构建 MCP 服务器

// ❌ Bad (STDIO)
console.log("Server started");

// ✅ Good (STDIO)
console.error("Server started"); // stderr is safe

node --version
npm --version

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { z } from "zod";

const NWS_API_BASE = "https://api.weather.gov";
const USER_AGENT = "weather-app/1.0";

// Create server instance
const server = new McpServer({
  name: "weather",
  version: "1.0.0",
});

// Helper function for making NWS API requests
async function makeNWSRequest<T>(url: string): Promise<T | null> {
  const headers = {
    "User-Agent": USER_AGENT,
    Accept: "application/geo+json",
  };

  try {
    const response = await fetch(url, { headers });
    if (!response.ok) {
      throw new Error(`HTTP error! status: ${response.status}`);
    }
    return (await response.json()) as T;
  } catch (error) {
    console.error("Error making NWS request:", error);
    return null;
  }
}

interface AlertFeature {
  properties: {
    event?: string;
    areaDesc?: string;
    severity?: string;
    status?: string;
    headline?: string;
  };
}

// Format alert data
function formatAlert(feature: AlertFeature): string {
  const props = feature.properties;
  return [
    `Event: ${props.event || "Unknown"}`,
    `Area: ${props.areaDesc || "Unknown"}`,
    `Severity: ${props.severity || "Unknown"}`,
    `Status: ${props.status || "Unknown"}`,
    `Headline: ${props.headline || "No headline"}`,
    "---",
  ].join("\n");
}

interface ForecastPeriod {
  name?: string;
  temperature?: number;
  temperatureUnit?: string;
  windSpeed?: string;
  windDirection?: string;
  shortForecast?: string;
}

interface AlertsResponse {
  features: AlertFeature[];
}

interface PointsResponse {
  properties: {
    forecast?: string;
  };
}

interface ForecastResponse {
  properties: {
    periods: ForecastPeriod[];
  };
}

// Register weather tools

server.registerTool(
  "get_alerts",
  {
    description: "Get weather alerts for a state",
    inputSchema: {
      state: z
        .string()
        .length(2)
        .describe("Two-letter state code (e.g. CA, NY)"),
    },
  },
  async ({ state }) => {
    const stateCode = state.toUpperCase();
    const alertsUrl = `${NWS_API_BASE}/alerts?area=${stateCode}`;
    const alertsData = await makeNWSRequest<AlertsResponse>(alertsUrl);

    if (!alertsData) {
      return {
        content: [
          {
            type: "text",
            text: "Failed to retrieve alerts data",
          },
        ],
      };
    }

    const features = alertsData.features || [];
    if (!features.length) {
      return {
        content: [
          {
            type: "text",
            text: `No active alerts for ${stateCode}`,
          },
        ],
      };
    }

    const formattedAlerts = features.map(formatAlert);
    const alertsText = `Active alerts for ${stateCode}:\n\n${formattedAlerts.join("\n")}`;

    return {
      content: [
        {
          type: "text",
          text: alertsText,
        },
      ],
    };
  },
);

server.registerTool(
  "get_forecast",
  {
    description: "Get weather forecast for a location",
    inputSchema: {
      latitude: z
        .number()
        .min(-90)
        .max(90)
        .describe("Latitude of the location"),
      longitude: z
        .number()
        .min(-180)
        .max(180)
        .describe("Longitude of the location"),
    },
  },
  async ({ latitude, longitude }) => {
    // Get grid point data
    const pointsUrl = `${NWS_API_BASE}/points/${latitude.toFixed(4)},${longitude.toFixed(4)}`;
    const pointsData = await makeNWSRequest<PointsResponse>(pointsUrl);

    if (!pointsData) {
      return {
        content: [
          {
            type: "text",
            text: `Failed to retrieve grid point data for coordinates: ${latitude}, ${longitude}. This location may not be supported by the NWS API (only US locations are supported).`,
          },
        ],
      };
    }

    const forecastUrl = pointsData.properties?.forecast;
    if (!forecastUrl) {
      return {
        content: [
          {
            type: "text",
            text: "Failed to get forecast URL from grid point data",
          },
        ],
      };
    }

    // Get forecast data
    const forecastData = await makeNWSRequest<ForecastResponse>(forecastUrl);
    if (!forecastData) {
      return {
        content: [
          {
            type: "text",
            text: "Failed to retrieve forecast data",
          },
        ],
      };
    }

    const periods = forecastData.properties?.periods || [];
    if (periods.length === 0) {
      return {
        content: [
          {
            type: "text",
            text: "No forecast periods available",
          },
        ],
      };
    }

    // Format forecast periods
    const formattedForecast = periods.map((period: ForecastPeriod) =>
      [
        `${period.name || "Unknown"}:`,
        `Temperature: ${period.temperature || "Unknown"}°${period.temperatureUnit || "F"}`,
        `Wind: ${period.windSpeed || "Unknown"} ${period.windDirection || ""}`,
        `${period.shortForecast || "No forecast available"}`,
        "---",
      ].join("\n"),
    );

    const forecastText = `Forecast for ${latitude}, ${longitude}:\n\n${formattedForecast.join("\n")}`;

    return {
      content: [
        {
          type: "text",
          text: forecastText,
        },
      ],
    };
  },
);

async function main() {
  const transport = new StdioServerTransport();
  await server.connect(transport);
  console.error("Weather MCP Server running on stdio");
}

main().catch((error) => {
  console.error("Fatal error in main():", error);
  process.exit(1);
});

@Service
public class WeatherService {

	private final RestClient restClient;

	public WeatherService() {
		this.restClient = RestClient.builder()
			.baseUrl("https://api.weather.gov")
			.defaultHeader("Accept", "application/geo+json")
			.defaultHeader("User-Agent", "WeatherApiClient/1.0 (your@email.com)")
			.build();
	}

  @Tool(description = "Get weather forecast for a specific latitude/longitude")
  public String getWeatherForecastByLocation(
      double latitude,   // Latitude coordinate
      double longitude   // Longitude coordinate
  ) {
      // Returns detailed forecast including:
      // - Temperature and unit
      // - Wind speed and direction
      // - Detailed forecast description
  }

  @Tool(description = "Get weather alerts for a US state")
  public String getAlerts(
      @ToolParam(description = "Two-letter US state code (e.g. CA, NY)") String state
  ) {
      // Returns active alerts including:
      // - Event type
      // - Affected area
      // - Severity
      // - Description
      // - Safety instructions
  }

  // ......
}

@SpringBootApplication
public class McpServerApplication {

	public static void main(String[] args) {
		SpringApplication.run(McpServerApplication.class, args);
	}

	@Bean
	public ToolCallbackProvider weatherTools(WeatherService weatherService) {
		return  MethodToolCallbackProvider.builder().toolObjects(weatherService).build();
	}
}

./mvnw clean install

var stdioParams = ServerParameters.builder("java")
  .args("-jar", "/ABSOLUTE/PATH/TO/PARENT/FOLDER/mcp-weather-stdio-server-0.0.1-SNAPSHOT.jar")
  .build();

var stdioTransport = new StdioClientTransport(stdioParams);

var mcpClient = McpClient.sync(stdioTransport).build();

mcpClient.initialize();

ListToolsResult toolsList = mcpClient.listTools();

CallToolResult weather = mcpClient.callTool(
  new CallToolRequest("getWeatherForecastByLocation",
      Map.of("latitude", "47.6062", "longitude", "-122.3321")));

CallToolResult alert = mcpClient.callTool(
  new CallToolRequest("getAlerts", Map.of("state", "NY")));

mcpClient.closeGracefully();

<dependency>
    <groupId>org.springframework.ai</groupId>
    <artifactId>spring-ai-starter-mcp-client</artifactId>
</dependency>

spring.ai.mcp.client.stdio.servers-configuration=file:PATH/TO/claude_desktop_config.json

java --version

./gradlew build

fun runMcpServer() {
    val server = Server(
        Implementation(
            name = "weather",
            version = "1.0.0",
        ),
        ServerOptions(
            capabilities = ServerCapabilities(tools = ServerCapabilities.Tools(listChanged = true)),
        ),
    )

    // register tools on server here

    val transport = StdioServerTransport(
        System.`in`.asInput(),
        System.out.asSink().buffered(),
    )

    runBlocking {
        val session = server.createSession(transport)
        val done = Job()
        session.onClose {
            done.complete()
        }
        done.join()
    }
}

val httpClient = HttpClient(CIO) {
    defaultRequest {
        url("https://api.weather.gov")
        headers {
            append("Accept", "application/geo+json")
            append("User-Agent", "WeatherApiClient/1.0")
        }
        contentType(ContentType.Application.Json)
    }
    install(ContentNegotiation) {
        json(Json { ignoreUnknownKeys = true })
    }
}

// Extension function to fetch weather alerts for a given state
suspend fun HttpClient.getAlerts(state: String): List<String> {
    val alerts = this.get("/alerts/active/area/$state").body<AlertsResponse>()
    return alerts.features.map { feature ->
        """
            Event: ${feature.properties.event}
            Area: ${feature.properties.areaDesc}
            Severity: ${feature.properties.severity}
            Status: ${feature.properties.status}
            Headline: ${feature.properties.headline}
        """.trimIndent()
    }
}

// Extension function to fetch forecast information for given latitude and longitude
suspend fun HttpClient.getForecast(latitude: Double, longitude: Double): List<String> {
    val points = this.get("/points/$latitude,$longitude").body<PointsResponse>()
    val forecastUrl = points.properties.forecast ?: error("No forecast URL available")
    val forecast = this.get(forecastUrl).body<ForecastResponse>()
    return forecast.properties.periods.map { period ->
        """
            ${period.name}:
            Temperature: ${period.temperature}°${period.temperatureUnit}
            Wind: ${period.windSpeed} ${period.windDirection}
            ${period.shortForecast}
        """.trimIndent()
    }
}

@Serializable
data class PointsResponse(val properties: PointsProperties)

@Serializable
data class PointsProperties(val forecast: String? = null)

@Serializable
data class ForecastResponse(val properties: ForecastProperties)

@Serializable
data class ForecastProperties(val periods: List<ForecastPeriod> = emptyList())

@Serializable
data class ForecastPeriod(
    val name: String? = null,
    val temperature: Int? = null,
    val temperatureUnit: String? = null,
    val windSpeed: String? = null,
    val windDirection: String? = null,
    val shortForecast: String? = null,
)

@Serializable
data class AlertsResponse(val features: List<AlertFeature> = emptyList())

@Serializable
data class AlertFeature(val properties: AlertProperties)

@Serializable
data class AlertProperties(
    val event: String? = null,
    val areaDesc: String? = null,
    val severity: String? = null,
    val status: String? = null,
    val headline: String? = null,
)

// Register weather tools

server.addTool(
    name = "get_alerts",
    description = "Get weather alerts for a US state. Input is a two-letter US state code (e.g. CA, NY)",
    inputSchema = ToolSchema(
        properties = buildJsonObject {
            putJsonObject("state") {
                put("type", "string")
                put("description", "Two-letter US state code (e.g. CA, NY)")
            }
        },
        required = listOf("state"),
    ),
) { request ->
    val state = request.arguments?.get("state")?.jsonPrimitive?.content
        ?: return@addTool CallToolResult(
            content = listOf(TextContent("The 'state' parameter is required.")),
        )

    val alerts = httpClient.getAlerts(state)
    CallToolResult(content = alerts.map { TextContent(it) })
}

server.addTool(
    name = "get_forecast",
    description = "Get weather forecast for a location. Note: only US locations are supported by the NWS API.",
    inputSchema = ToolSchema(
        properties = buildJsonObject {
            putJsonObject("latitude") {
                put("type", "number")
                put("description", "Latitude of the location")
            }
            putJsonObject("longitude") {
                put("type", "number")
                put("description", "Longitude of the location")
            }
        },
        required = listOf("latitude", "longitude"),
    ),
) { request ->
    val latitude = request.arguments?.get("latitude")?.jsonPrimitive?.doubleOrNull
    val longitude = request.arguments?.get("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) })
}

fun main() = runMcpServer()

./gradlew run

./gradlew build
java -jar build/libs/weather-0.1.0-all.jar

dotnet --version

# Add the Model Context Protocol SDK NuGet package
dotnet add package ModelContextProtocol --prerelease
# Add the .NET Hosting NuGet package
dotnet add package Microsoft.Extensions.Hosting

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using ModelContextProtocol;
using System.Net.Http.Headers;

var builder = Host.CreateEmptyApplicationBuilder(settings: null);

builder.Services.AddMcpServer()
    .WithStdioServerTransport()
    .WithToolsFromAssembly();

builder.Services.AddSingleton(_ =>
{
    var client = new HttpClient() { BaseAddress = new Uri("https://api.weather.gov") };
    client.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue("weather-tool", "1.0"));
    return client;
});

var app = builder.Build();

await app.RunAsync();

using System.Text.Json;

internal static class HttpClientExt
{
    public static async Task<JsonDocument> ReadJsonDocumentAsync(this HttpClient client, string requestUri)
    {
        using var response = await client.GetAsync(requestUri);
        response.EnsureSuccessStatusCode();
        return await JsonDocument.ParseAsync(await response.Content.ReadAsStreamAsync());
    }
}

using ModelContextProtocol.Server;
using System.ComponentModel;
using System.Globalization;
using System.Text.Json;

namespace QuickstartWeatherServer.Tools;

[McpServerToolType]
public static class WeatherTools
{
    [McpServerTool, Description("Get weather alerts for a US state code.")]
    public static async Task<string> GetAlerts(
        HttpClient client,
        [Description("The US state code to get alerts for.")] string state)
    {
        using var jsonDocument = await client.ReadJsonDocumentAsync($"/alerts/active/area/{state}");
        var jsonElement = jsonDocument.RootElement;
        var alerts = jsonElement.GetProperty("features").EnumerateArray();

        if (!alerts.Any())
        {
            return "No active alerts for this state.";
        }

        return string.Join("\n--\n", alerts.Select(alert =>
        {
            JsonElement properties = alert.GetProperty("properties");
            return $"""
                    Event: {properties.GetProperty("event").GetString()}
                    Area: {properties.GetProperty("areaDesc").GetString()}
                    Severity: {properties.GetProperty("severity").GetString()}
                    Description: {properties.GetProperty("description").GetString()}
                    Instruction: {properties.GetProperty("instruction").GetString()}
                    """;
        }));
    }

    [McpServerTool, Description("Get weather forecast for a location.")]
    public static async Task<string> GetForecast(
        HttpClient client,
        [Description("Latitude of the location.")] double latitude,
        [Description("Longitude of the location.")] double longitude)
    {
        var pointUrl = string.Create(CultureInfo.InvariantCulture, $"/points/{latitude},{longitude}");
        using var jsonDocument = await client.ReadJsonDocumentAsync(pointUrl);
        var forecastUrl = jsonDocument.RootElement.GetProperty("properties").GetProperty("forecast").GetString()
            ?? throw new Exception($"No forecast URL provided by {client.BaseAddress}points/{latitude},{longitude}");

        using var forecastDocument = await client.ReadJsonDocumentAsync(forecastUrl);
        var periods = forecastDocument.RootElement.GetProperty("properties").GetProperty("periods").EnumerateArray();

        return string.Join("\n---\n", periods.Select(period => $"""
                {period.GetProperty("name").GetString()}
                Temperature: {period.GetProperty("temperature").GetInt32()}°F
                Wind: {period.GetProperty("windSpeed").GetString()} {period.GetProperty("windDirection").GetString()}
                Forecast: {period.GetProperty("detailedForecast").GetString()}
                """));
    }
}

dotnet run

# ❌ Bad (STDIO)
puts "Processing request"

# ✅ Good (STDIO)
require "logger"
logger = Logger.new($stderr)
logger.info("Processing request")

ruby --version

require "json"
require "mcp"
require "net/http"
require "uri"

NWS_API_BASE = "https://api.weather.gov"
USER_AGENT = "weather-app/1.0"

module HelperMethods
  def make_nws_request(url)
    uri = URI(url)
    request = Net::HTTP::Get.new(uri)
    request["User-Agent"] = USER_AGENT
    request["Accept"] = "application/geo+json"

    response = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) do |http|
      http.request(request)
    end

    raise "HTTP #{response.code}: #{response.message}" unless response.is_a?(Net::HTTPSuccess)

    JSON.parse(response.body)
  end

  def format_alert(feature)
    properties = feature["properties"]

    <<~ALERT
      Event: #{properties["event"] || "Unknown"}
      Area: #{properties["areaDesc"] || "Unknown"}
      Severity: #{properties["severity"] || "Unknown"}
      Description: #{properties["description"] || "No description available"}
      Instructions: #{properties["instruction"] || "No specific instructions provided"}
    ALERT
  end
end

class GetAlerts < MCP::Tool
  extend HelperMethods

  tool_name "get_alerts"
  description "Get weather alerts for a US state"
  input_schema(
    properties: {
      state: {
        type: "string",
        description: "Two-letter US state code (e.g. CA, NY)"
      }
    },
    required: ["state"]
  )

  def self.call(state:)
    url = "#{NWS_API_BASE}/alerts/active/area/#{state.upcase}"
    data = make_nws_request(url)

    if data["features"].empty?
      return MCP::Tool::Response.new([{
        type: "text",
        text: "No active alerts for this state."
      }])
    end

    alerts = data["features"].map { |feature| format_alert(feature) }
    MCP::Tool::Response.new([{
      type: "text",
      text: alerts.join("\n---\n")
    }])
  end
end

class GetForecast < MCP::Tool
  extend HelperMethods

  tool_name "get_forecast"
  description "Get weather forecast for a location"
  input_schema(
    properties: {
      latitude: {
        type: "number",
        description: "Latitude of the location"
      },
      longitude: {
        type: "number",
        description: "Longitude of the location"
      }
    },
    required: ["latitude", "longitude"]
  )

  def self.call(latitude:, longitude:)
    # First get the forecast grid endpoint.
    points_url = "#{NWS_API_BASE}/points/#{latitude},#{longitude}"
    points_data = make_nws_request(points_url)

    # Get the forecast URL from the points response.
    forecast_url = points_data["properties"]["forecast"]
    forecast_data = make_nws_request(forecast_url)

    # Format the periods into a readable forecast.
    periods = forecast_data["properties"]["periods"]
    forecasts = periods.first(5).map do |period|
      <<~FORECAST
        #{period["name"]}:
        Temperature: #{period["temperature"]}°#{period["temperatureUnit"]}
        Wind: #{period["windSpeed"]} #{period["windDirection"]}
        Forecast: #{period["detailedForecast"]}
      FORECAST
    end

    MCP::Tool::Response.new([{
      type: "text",
      text: forecasts.join("\n---\n")
    }])
  end
end

server = MCP::Server.new(
  name: "weather",
  version: "1.0.0",
  tools: [GetAlerts, GetForecast]
)

transport = MCP::Server::Transports::StdioTransport.new(server)
transport.open

// ❌ Bad (STDIO)
println!("Processing request");

// ✅ Good (STDIO)
eprintln!("Processing request"); // writes to stderr

rustc --version
cargo --version