diff --git a/cmd/mtc/main.go b/cmd/mtc/main.go
index d76908f..2d4d781 100644
--- a/cmd/mtc/main.go
+++ b/cmd/mtc/main.go
@@ -1,29 +1,30 @@
 package main
 
 import (
-	"errors"
-	"maps"
-	"slices"
-
-	"github.com/bwesterb/mtc"
-	"github.com/bwesterb/mtc/ca"
-	"github.com/bwesterb/mtc/mirror"
-	"github.com/bwesterb/mtc/umbilical"
-	"github.com/bwesterb/mtc/umbilical/frozencas"
-	"github.com/urfave/cli/v2"
-	"golang.org/x/crypto/cryptobyte"
-
 	"bufio"
 	"crypto/x509"
 	"encoding/hex"
 	"encoding/pem"
+	"errors"
 	"fmt"
 	"io"
+	"maps"
 	"net"
 	"os"
 	"runtime/pprof"
+	"slices"
+	"strings"
 	"text/tabwriter"
 	"time"
+
+	"github.com/bwesterb/mtc"
+	"github.com/bwesterb/mtc/ca"
+	"github.com/bwesterb/mtc/mirror"
+	"github.com/bwesterb/mtc/umbilical"
+	"github.com/bwesterb/mtc/umbilical/frozencas"
+
+	"github.com/urfave/cli/v2"
+	"golang.org/x/crypto/cryptobyte"
 )
 
 var (
@@ -1085,8 +1086,30 @@ func handleInspectCaParams(cc *cli.Context) error {
 	return nil
 }
 
+var appDescription = strings.TrimSpace(`
+This utility provides various functions to work with Merkle Tree Certificates.
+See http://github.com/bwesterb/mtc/ for an introduction.
+
+Commands under "mtc ca" are used to manage a Merkle Tree CA.
+"mtc ca new" creates a CA.  "mtc ca queue" queues an assertion to be
+certified.  "mtc ca issue" issues a batch.  See "mtc ca -h" for more
+commands and info.
+
+Commands under  "mtc mirror" are used to manage a mirror of a Merkle Tree CA.
+"mtc mirror new" sets up a new mirror and "mtc mirror update" syncs it
+with the upstream CA.  See "mtc mirror -h" for more commands and info.
+
+Commands under "mtc inspect" allow you to investigate the contents
+of Merkle Tree Certificates and various other files present in a CA / mirror.
+
+With "mtc new-assertion-request" you can create a request for a new
+Merkle Tree Certificate that can be sent to a CA.
+`)
+
 func main() {
 	app := &cli.App{
+		Usage:       "Merkle Tree Certificates utility",
+		Description: appDescription,
 		Flags: []cli.Flag{
 			&cli.StringFlag{
 				Name:  "cpuprofile",
@@ -1095,7 +1118,8 @@ func main() {
 		},
 		Commands: []*cli.Command{
 			{
-				Name: "ca",
+				Name:  "ca",
+				Usage: "manage CA",
 				Flags: []cli.Flag{
 					&cli.StringFlag{
 						Name:    "ca-path",
@@ -1206,7 +1230,8 @@ func main() {
 				},
 			},
 			{
-				Name: "mirror",
+				Name:  "mirror",
+				Usage: "manage mirror of a CA",
 				Flags: []cli.Flag{
 					&cli.StringFlag{
 						Name:    "mirror-path",
@@ -1244,7 +1269,8 @@ func main() {
 				},
 			},
 			{
-				Name: "inspect",
+				Name:  "inspect",
+				Usage: "inspect various MTC related binary files",
 				Subcommands: []*cli.Command{
 					{
 						Name:      "ca-params",