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Add weather-server-go
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‎weather-server-go/README.md‎

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# A Simple MCP Weather Server written in Go
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See the [Quickstart](https://modelcontextprotocol.io/quickstart) tutorial for more information.
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## Building
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```bash
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go build -o weather
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```
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## Running
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```bash
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./weather
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```
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The server will communicate via stdio and expose two MCP tools:
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- `get_forecast` - Get weather forecast for a location (requires latitude and longitude)
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- `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
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go 1.25.1
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require github.com/modelcontextprotocol/go-sdk v1.0.0
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require (
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github.com/google/jsonschema-go v0.3.0 // indirect
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github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
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)

‎weather-server-go/go.sum‎

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

‎weather-server-go/main.go‎

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

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