diff --git a/cmd/tg/app.go b/cmd/tg/app.go
index 895e7a1..4936236 100644
--- a/cmd/tg/app.go
+++ b/cmd/tg/app.go
@@ -14,6 +14,7 @@ import (
 	"golang.org/x/xerrors"
 	"gopkg.in/yaml.v3"
 
+	"github.com/gotd/cli/internal/pretty"
 	"github.com/gotd/td/session"
 	"github.com/gotd/td/telegram"
 	"github.com/gotd/td/telegram/dcs"
@@ -25,6 +26,8 @@ type app struct {
 	cfg  Config
 	log  *zap.Logger
 	opts telegram.Options
+
+	debugInvoker bool
 }
 
 func newApp() *app {
@@ -59,17 +62,20 @@ func (p *app) run(ctx context.Context, f func(ctx context.Context, api *tg.Clien
 			}
 		}
 
-		invoker := invokers.NewWaiter(client)
-		raw := tg.NewClient(invoker)
-
 		ctx, cancel := context.WithCancel(ctx)
 		g, ctx := errgroup.WithContext(ctx)
+
+		invoker := invokers.NewWaiter(client)
 		g.Go(func() error {
 			return invoker.Run(ctx)
 		})
 		g.Go(func() error {
 			defer cancel()
-			return f(ctx, raw)
+			var i tg.Invoker = invoker
+			if p.debugInvoker {
+				i = pretty.Invoker{Next: i}
+			}
+			return f(ctx, tg.NewClient(i))
 		})
 
 		if err := g.Wait(); !errors.Is(err, context.Canceled) {
@@ -113,6 +119,9 @@ func (p *app) Before(c *cli.Context) error {
 	if c.Bool("test") {
 		p.opts.DCList = dcs.StagingDCs()
 	}
+	if c.Bool("debug-invoker") {
+		p.debugInvoker = true
+	}
 
 	return nil
 }
diff --git a/cmd/tg/main.go b/cmd/tg/main.go
index 422f367..381a0dc 100644
--- a/cmd/tg/main.go
+++ b/cmd/tg/main.go
@@ -37,6 +37,10 @@ func main() {
 				Value:   defaultConfigPath(),
 				Usage:   "config to use",
 			},
+			&cli.BoolFlag{
+				Name:  "debug-invoker",
+				Usage: "use pretty-printing debug invoker",
+			},
 			&cli.BoolFlag{
 				Name:    "test",
 				Aliases: []string{"staging"},
diff --git a/internal/pretty/pretty.go b/internal/pretty/pretty.go
new file mode 100644
index 0000000..aabf736
--- /dev/null
+++ b/internal/pretty/pretty.go
@@ -0,0 +1,46 @@
+// Package pretty implements pretty-print facilities.
+package pretty
+
+import (
+	"context"
+	"fmt"
+	"reflect"
+	"time"
+
+	"github.com/gotd/td/bin"
+	"github.com/gotd/td/tdp"
+	"github.com/gotd/td/tg"
+)
+
+type Invoker struct {
+	Next tg.Invoker
+}
+
+func formatObject(input interface{}) string {
+	o, ok := input.(tdp.Object)
+	if !ok {
+		// Handle tg.*Box values.
+		rv := reflect.Indirect(reflect.ValueOf(input))
+		for i := 0; i < rv.NumField(); i++ {
+			if v, ok := rv.Field(i).Interface().(tdp.Object); ok {
+				return formatObject(v)
+			}
+		}
+
+		return fmt.Sprintf("%T (not object)", input)
+	}
+	return tdp.Format(o)
+}
+
+func (i Invoker) InvokeRaw(ctx context.Context, input bin.Encoder, output bin.Decoder) error {
+	fmt.Println("→", formatObject(input))
+	start := time.Now()
+	if err := i.Next.InvokeRaw(ctx, input, output); err != nil {
+		fmt.Println("←", err)
+		return err
+	}
+
+	fmt.Printf("← (%s) %s\n", time.Since(start).Round(time.Millisecond), formatObject(output))
+
+	return nil
+}