diff --git a/cmd/email-mcp/main.go b/cmd/email-mcp/main.go
new file mode 100644
index 0000000..4a8b2e8
--- /dev/null
+++ b/cmd/email-mcp/main.go
@@ -0,0 +1,16 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"email-mcp/internal/cli"
+)
+
+func main() {
+	app := cli.NewApp(nil, nil, nil, nil)
+	if err := app.Run(os.Args[1:]); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..75616fa
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module email-mcp
+
+go 1.25.0
diff --git a/internal/cli/app.go b/internal/cli/app.go
new file mode 100644
index 0000000..03db9ea
--- /dev/null
+++ b/internal/cli/app.go
@@ -0,0 +1,22 @@
+package cli
+
+import "fmt"
+
+type App struct{}
+
+func NewApp(_, _, _, _ any) *App {
+	return &App{}
+}
+
+func (a *App) Run(args []string) error {
+	if len(args) == 0 {
+		return fmt.Errorf("usage: email-mcp <setup|mcp>")
+	}
+
+	switch args[0] {
+	case "setup", "mcp":
+		return nil
+	default:
+		return fmt.Errorf("unknown command: %s", args[0])
+	}
+}
diff --git a/internal/cli/app_test.go b/internal/cli/app_test.go
new file mode 100644
index 0000000..1bd1eb3
--- /dev/null
+++ b/internal/cli/app_test.go
@@ -0,0 +1,27 @@
+package cli
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestAppRunRejectsUnknownCommand(t *testing.T) {
+	app := NewApp(nil, nil, nil, nil)
+
+	err := app.Run([]string{"unknown"})
+	if err == nil {
+		t.Fatal("expected error for unknown command")
+	}
+}
+
+func TestAppRunShowsUsageWhenNoArgsProvided(t *testing.T) {
+	app := NewApp(nil, nil, nil, nil)
+
+	err := app.Run(nil)
+	if err == nil {
+		t.Fatal("expected error for missing command")
+	}
+	if !strings.Contains(err.Error(), "usage:") {
+		t.Fatalf("expected usage text in error, got %q", err.Error())
+	}
+}