Add weather-server-go

weather-server-go/README.md

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+# A Simple MCP Weather Server written in Go
+
+See the [Quickstart](https://modelcontextprotocol.io/quickstart) tutorial for more information.
+
+## Building
+
+```bash
+go build -o weather
+```
+
+## Running
+
+```bash
+./weather
+```
+
+The server will communicate via stdio and expose two MCP tools:
+- `get_forecast` - Get weather forecast for a location (requires latitude and longitude)
+- `get_alerts` - Get weather alerts for a US state (requires two-letter state code)

weather-server-go/go.mod

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+module github.com/modelcontextprotocol/quickstart-resources/weather-server-go
+
+go 1.25.1
+
+require github.com/modelcontextprotocol/go-sdk v1.0.0
+
+require (
+	github.com/google/jsonschema-go v0.3.0 // indirect
+	github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
+)

weather-server-go/go.sum

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+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
+github.com/google/jsonschema-go v0.3.0 h1:6AH2TxVNtk3IlvkkhjrtbUc4S8AvO0Xii0DxIygDg+Q=
+github.com/google/jsonschema-go v0.3.0/go.mod h1:r5quNTdLOYEz95Ru18zA0ydNbBuYoo9tgaYcxEYhJVE=
+github.com/modelcontextprotocol/go-sdk v1.0.0 h1:Z4MSjLi38bTgLrd/LjSmofqRqyBiVKRyQSJgw8q8V74=
+github.com/modelcontextprotocol/go-sdk v1.0.0/go.mod h1:nYtYQroQ2KQiM0/SbyEPUWQ6xs4B95gJjEalc9AQyOs=
+github.com/yosida95/uritemplate/v3 v3.0.2 h1:Ed3Oyj9yrmi9087+NczuL5BwkIc4wvTb5zIM+UJPGz4=
+github.com/yosida95/uritemplate/v3 v3.0.2/go.mod h1:ILOh0sOhIJR3+L/8afwt/kE++YT040gmv5BQTMR2HP4=
+golang.org/x/tools v0.34.0 h1:qIpSLOxeCYGg9TrcJokLBG4KFA6d795g0xkBkiESGlo=
+golang.org/x/tools v0.34.0/go.mod h1:pAP9OwEaY1CAW3HOmg3hLZC5Z0CCmzjAF2UQMSqNARg=

weather-server-go/main.go

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+package main
+
+import (
+	"cmp"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"strings"
+
+	"github.com/modelcontextprotocol/go-sdk/mcp"
+)
+
+const (
+	NWSAPIBase = "https://api.weather.gov"
+	UserAgent  = "weather-app/1.0"
+)
+
+type ForecastInput struct {
+	Latitude  float64 `json:"latitude" jsonschema:"Latitude of the location"`
+	Longitude float64 `json:"longitude" jsonschema:"Longitude of the location"`
+}
+
+type AlertsInput struct {
+	State string `json:"state" jsonschema:"Two-letter US state code (e.g. CA, NY)"`
+}
+
+type PointsResponse struct {
+	Properties struct {
+		Forecast string `json:"forecast"`
+	} `json:"properties"`
+}
+
+type ForecastResponse struct {
+	Properties struct {
+		Periods []ForecastPeriod `json:"periods"`
+	} `json:"properties"`
+}
+
+type ForecastPeriod struct {
+	Name             string `json:"name"`
+	Temperature      int    `json:"temperature"`
+	TemperatureUnit  string `json:"temperatureUnit"`
+	WindSpeed        string `json:"windSpeed"`
+	WindDirection    string `json:"windDirection"`
+	DetailedForecast string `json:"detailedForecast"`
+}
+
+type AlertsResponse struct {
+	Features []AlertFeature `json:"features"`
+}
+
+type AlertFeature struct {
+	Properties AlertProperties `json:"properties"`
+}
+
+type AlertProperties struct {
+	Event       string `json:"event"`
+	AreaDesc    string `json:"areaDesc"`
+	Severity    string `json:"severity"`
+	Description string `json:"description"`
+	Instruction string `json:"instruction"`
+}
+
+func makeNWSRequest[T any](ctx context.Context, url string) (*T, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+
+	req.Header.Set("User-Agent", UserAgent)
+	req.Header.Set("Accept", "application/geo+json")
+
+	client := &http.Client{}
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("failed to make request to %s: %w", url, err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		body, _ := io.ReadAll(resp.Body)
+		return nil, fmt.Errorf("HTTP error %d: %s", resp.StatusCode, string(body))
+	}
+
+	var result T
+	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+		return nil, fmt.Errorf("failed to decode response: %w", err)
+	}
+
+	return &result, nil
+}
+
+func formatAlert(alert AlertFeature) string {
+	props := alert.Properties
+	event := cmp.Or(props.Event, "Unknown")
+	areaDesc := cmp.Or(props.AreaDesc, "Unknown")
+	severity := cmp.Or(props.Severity, "Unknown")
+	description := cmp.Or(props.Description, "No description available")
+	instruction := cmp.Or(props.Instruction, "No specific instructions provided")
+
+	return fmt.Sprintf(`
+Event: %s
+Area: %s
+Severity: %s
+Description: %s
+Instructions: %s
+`, event, areaDesc, severity, description, instruction)
+}
+
+func formatPeriod(period ForecastPeriod) string {
+	return fmt.Sprintf(`
+%s:
+Temperature: %d°%s
+Wind: %s %s
+Forecast: %s
+`, period.Name, period.Temperature, period.TemperatureUnit,
+		period.WindSpeed, period.WindDirection, period.DetailedForecast)
+}
+
+func getForecast(ctx context.Context, req *mcp.CallToolRequest, input ForecastInput) (
+	*mcp.CallToolResult, any, error,
+) {
+	// Get points data
+	pointsURL := fmt.Sprintf("%s/points/%f,%f", NWSAPIBase, input.Latitude, input.Longitude)
+	pointsData, err := makeNWSRequest[PointsResponse](ctx, pointsURL)
+	if err != nil {
+		return &mcp.CallToolResult{
+			Content: []mcp.Content{
+				&mcp.TextContent{Text: "Unable to fetch forecast data for this location."},
+			},
+		}, nil, nil
+	}
+
+	// Get forecast data
+	forecastURL := pointsData.Properties.Forecast
+	if forecastURL == "" {
+		return &mcp.CallToolResult{
+			Content: []mcp.Content{
+				&mcp.TextContent{Text: "Unable to fetch forecast URL."},
+			},
+		}, nil, nil
+	}
+
+	forecastData, err := makeNWSRequest[ForecastResponse](ctx, forecastURL)
+	if err != nil {
+		return &mcp.CallToolResult{
+			Content: []mcp.Content{
+				&mcp.TextContent{Text: "Unable to fetch detailed forecast."},
+			},
+		}, nil, nil
+	}
+
+	// Format the periods
+	periods := forecastData.Properties.Periods
+	if len(periods) == 0 {
+		return &mcp.CallToolResult{
+			Content: []mcp.Content{
+				&mcp.TextContent{Text: "No forecast periods available."},
+			},
+		}, nil, nil
+	}
+
+	// Show next 5 periods
+	var forecasts []string
+	for i := range min(5, len(periods)) {
+		forecasts = append(forecasts, formatPeriod(periods[i]))
+	}
+
+	result := strings.Join(forecasts, "\n---\n")
+
+	return &mcp.CallToolResult{
+		Content: []mcp.Content{
+			&mcp.TextContent{Text: result},
+		},
+	}, nil, nil
+}
+
+func getAlerts(ctx context.Context, req *mcp.CallToolRequest, input AlertsInput) (
+	*mcp.CallToolResult, any, error,
+) {
+	// Build alerts URL
+	stateCode := strings.ToUpper(input.State)
+	alertsURL := fmt.Sprintf("%s/alerts/active/area/%s", NWSAPIBase, stateCode)
+
+	alertsData, err := makeNWSRequest[AlertsResponse](ctx, alertsURL)
+	if err != nil {
+		return &mcp.CallToolResult{
+			Content: []mcp.Content{
+				&mcp.TextContent{Text: "Unable to fetch alerts or no alerts found."},
+			},
+		}, nil, nil
+	}
+
+	// Check if there are any alerts
+	if len(alertsData.Features) == 0 {
+		return &mcp.CallToolResult{
+			Content: []mcp.Content{
+				&mcp.TextContent{Text: "No active alerts for this state."},
+			},
+		}, nil, nil
+	}
+
+	// Format alerts
+	var alerts []string
+	for _, feature := range alertsData.Features {
+		alerts = append(alerts, formatAlert(feature))
+	}
+
+	result := strings.Join(alerts, "\n---\n")
+
+	return &mcp.CallToolResult{
+		Content: []mcp.Content{
+			&mcp.TextContent{Text: result},
+		},
+	}, nil, nil
+}
+
+func main() {
+	// Create MCP server
+	server := mcp.NewServer(&mcp.Implementation{
+		Name:    "weather",
+		Version: "1.0.0",
+	}, nil)
+
+	// Add get_forecast tool
+	mcp.AddTool(server, &mcp.Tool{
+		Name:        "get_forecast",
+		Description: "Get weather forecast for a location",
+	}, getForecast)
+
+	// Add get_alerts tool
+	mcp.AddTool(server, &mcp.Tool{
+		Name:        "get_alerts",
+		Description: "Get weather alerts for a US state",
+	}, getAlerts)
+
+	// Run server on stdio transport
+	if err := server.Run(context.Background(), &mcp.StdioTransport{}); err != nil {
+		log.Fatal(err)
+	}
+}