diff --git a/driver.go b/driver.go
index e1246af..86f56da 100644
--- a/driver.go
+++ b/driver.go
@@ -496,16 +496,21 @@ func (wd *remoteWD) AppAuthReset(resource ProtectedResource) (err error) {
 	return
 }
 
-func (wd *remoteWD) Tap(x, y int) error {
-	return wd.TapFloat(float64(x), float64(y))
+func (wd *remoteWD) Tap(x, y int, options ...DataOption) error {
+	return wd.TapFloat(float64(x), float64(y), options...)
 }
 
-func (wd *remoteWD) TapFloat(x, y float64) (err error) {
+func (wd *remoteWD) TapFloat(x, y float64, options ...DataOption) (err error) {
 	// [[FBRoute POST:@"/wda/tap/:uuid"] respondWithTarget:self action:@selector(handleTap:)]
 	data := map[string]interface{}{
 		"x": x,
 		"y": y,
 	}
+	// append options in post data for extra WDA configurations
+	// e.g. add identifier in tap event logs
+	for _, option := range options {
+		option(data)
+	}
 	_, err = wd.executePost(data, "/session", wd.sessionId, "/wda/tap/0")
 	return
 }
@@ -542,11 +547,11 @@ func (wd *remoteWD) TouchAndHoldFloat(x, y float64, second ...float64) (err erro
 	return
 }
 
-func (wd *remoteWD) Drag(fromX, fromY, toX, toY int, pressForDuration ...float64) error {
-	return wd.DragFloat(float64(fromX), float64(fromY), float64(toX), float64(toY), pressForDuration...)
+func (wd *remoteWD) Drag(fromX, fromY, toX, toY int, options ...DataOption) error {
+	return wd.DragFloat(float64(fromX), float64(fromY), float64(toX), float64(toY), options...)
 }
 
-func (wd *remoteWD) DragFloat(fromX, fromY, toX, toY float64, pressForDuration ...float64) (err error) {
+func (wd *remoteWD) DragFloat(fromX, fromY, toX, toY float64, options ...DataOption) (err error) {
 	// [[FBRoute POST:@"/wda/dragfromtoforduration"] respondWithTarget:self action:@selector(handleDragCoordinate:)]
 	data := map[string]interface{}{
 		"fromX": fromX,
@@ -554,20 +559,28 @@ func (wd *remoteWD) DragFloat(fromX, fromY, toX, toY float64, pressForDuration .
 		"toX":   toX,
 		"toY":   toY,
 	}
-	if len(pressForDuration) == 0 || pressForDuration[0] < 0 {
-		pressForDuration = []float64{1.0}
+
+	// append options in post data for extra WDA configurations
+	// e.g. use WithPressDuration to set pressForDuration
+	for _, option := range options {
+		option(data)
+	}
+
+	if _, ok := data["duration"]; !ok {
+		data["duration"] = 1.0 // default duration
 	}
-	data["duration"] = pressForDuration[0]
 	_, err = wd.executePost(data, "/session", wd.sessionId, "/wda/dragfromtoforduration")
 	return
 }
 
-func (wd *remoteWD) Swipe(fromX, fromY, toX, toY int) error {
-	return wd.SwipeFloat(float64(fromX), float64(fromY), float64(toX), float64(toY))
+func (wd *remoteWD) Swipe(fromX, fromY, toX, toY int, options ...DataOption) error {
+	options = append(options, WithPressDuration(0))
+	return wd.SwipeFloat(float64(fromX), float64(fromY), float64(toX), float64(toY), options...)
 }
 
-func (wd *remoteWD) SwipeFloat(fromX, fromY, toX, toY float64) error {
-	return wd.DragFloat(fromX, fromY, toX, toY, 0)
+func (wd *remoteWD) SwipeFloat(fromX, fromY, toX, toY float64, options ...DataOption) error {
+	options = append(options, WithPressDuration(0))
+	return wd.DragFloat(fromX, fromY, toX, toY, options...)
 }
 
 func (wd *remoteWD) ForceTouch(x, y int, pressure float64, second ...float64) error {
@@ -624,13 +637,19 @@ func (wd *remoteWD) GetPasteboard(contentType PasteboardType) (raw *bytes.Buffer
 	return
 }
 
-func (wd *remoteWD) SendKeys(text string, frequency ...int) (err error) {
+func (wd *remoteWD) SendKeys(text string, options ...DataOption) (err error) {
 	// [[FBRoute POST:@"/wda/keys"] respondWithTarget:self action:@selector(handleKeys:)]
 	data := map[string]interface{}{"value": strings.Split(text, "")}
-	if len(frequency) == 0 || frequency[0] <= 0 {
-		frequency = []int{60}
+
+	// append options in post data for extra WDA configurations
+	// e.g. use WithFrequency to set frequency of typing
+	for _, option := range options {
+		option(data)
+	}
+
+	if _, ok := data["frequency"]; !ok {
+		data["frequency"] = 60 // default frequency
 	}
-	data["frequency"] = frequency[0]
 	_, err = wd.executePost(data, "/session", wd.sessionId, "/wda/keys")
 	return
 }
diff --git a/driver_test.go b/driver_test.go
index 6f380dc..817d96e 100644
--- a/driver_test.go
+++ b/driver_test.go
@@ -454,7 +454,7 @@ func Test_remoteWD_TouchAndHold(t *testing.T) {
 func Test_remoteWD_Drag(t *testing.T) {
 	setup(t)
 
-	// err := driver.Drag(200, 300, 200, 500, -1)
+	// err := driver.Drag(200, 300, 200, 500, WithPressDuration(0.5))
 	err := driver.Swipe(200, 300, 200, 500)
 	if err != nil {
 		t.Fatal(err)
@@ -511,7 +511,7 @@ func Test_remoteWD_SendKeys(t *testing.T) {
 	setup(t)
 
 	err := driver.SendKeys("App Store")
-	// err := driver.SendKeys("App Store", 3)
+	// err := driver.SendKeys("App Store", WithFrequency(3))
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/element.go b/element.go
index a17359c..a9573f2 100644
--- a/element.go
+++ b/element.go
@@ -9,9 +9,12 @@ import (
 	"strings"
 )
 
+// All elements returned by search endpoints have assigned element_id.
+// Given element_id you can query properties like:
+// enabled, rect, size, location, text, displayed, accessible, name
 type remoteWE struct {
 	parent *remoteWD
-	id     string
+	id     string // element_id
 }
 
 func (we remoteWE) Click() (err error) {
diff --git a/element_test.go b/element_test.go
index 932ff9e..931c758 100644
--- a/element_test.go
+++ b/element_test.go
@@ -155,6 +155,9 @@ func Test_remoteWE_PickerWheelSelect(t *testing.T) {
 	element := setupElement(t, BySelector{ClassName: ElementType{PickerWheel: true}})
 
 	err := element.PickerWheelSelect(PickerWheelOrderNext, 3)
+	if err != nil {
+		t.Fatal(err)
+	}
 	err = element.PickerWheelSelect(PickerWheelOrderPrevious)
 	if err != nil {
 		t.Fatal(err)
@@ -236,7 +239,13 @@ func Test_remoteWE_Rect(t *testing.T) {
 	element := setupElement(t, BySelector{ClassName: ElementType{Switch: true}})
 
 	rect, err := element.Rect()
+	if err != nil {
+		t.Fatal(err)
+	}
 	location, err := element.Location()
+	if err != nil {
+		t.Fatal(err)
+	}
 	size, err := element.Size()
 	if err != nil {
 		t.Fatal(err)
diff --git a/examples/keyboard/main.go b/examples/keyboard/main.go
index 8016d95..485521d 100644
--- a/examples/keyboard/main.go
+++ b/examples/keyboard/main.go
@@ -1,8 +1,9 @@
 package main
 
 import (
-	"github.com/electricbubble/gwda"
 	"log"
+
+	"github.com/electricbubble/gwda"
 )
 
 func main() {
@@ -16,6 +17,12 @@ func main() {
 		log.Fatalln(err)
 	}
 
+	// send keys with specified frequency
+	err = driver.SendKeys("world", gwda.WithFrequency(30))
+	if err != nil {
+		log.Fatalln(err)
+	}
+
 	// element, err := driver.ActiveElement()
 	// if err != nil {
 	// 	log.Fatalln(err)
diff --git a/examples/touch/main.go b/examples/touch/main.go
index 00f0e50..2164ae4 100644
--- a/examples/touch/main.go
+++ b/examples/touch/main.go
@@ -1,8 +1,9 @@
 package main
 
 import (
-	"github.com/electricbubble/gwda"
 	"log"
+
+	"github.com/electricbubble/gwda"
 )
 
 func main() {
@@ -18,6 +19,16 @@ func main() {
 		log.Fatalln(err)
 	}
 
+	// tap action with specified identifier
+	option := gwda.WithCustomOption("log", map[string]interface{}{
+		"enable": true,
+		"data":   "identifier-tap-A",
+	})
+	err = driver.Tap(x, y, option)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
 	err = driver.DoubleTap(x, y)
 	if err != nil {
 		log.Fatalln(err)
@@ -35,11 +46,31 @@ func main() {
 		log.Fatalln(err)
 	}
 
+	// drag action with specified identifier
+	option = gwda.WithCustomOption("log", map[string]interface{}{
+		"enable": true,
+		"data":   "identifier-drag-B",
+	})
+	err = driver.Drag(fromX, fromY, toX, toY, option)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
 	err = driver.Swipe(fromX, fromY, toX, toY)
 	if err != nil {
 		log.Fatalln(err)
 	}
 
+	// swipe action with specified identifier
+	option = gwda.WithCustomOption("log", map[string]interface{}{
+		"enable": true,
+		"data":   "identifier-swipe-C",
+	})
+	err = driver.Swipe(fromX, fromY, toX, toY, option)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
 	// 需要 3D Touch 硬件支持
 	// err = driver.ForceTouch(x, y, 0.8)
 	// if err != nil {
diff --git a/gwda.go b/gwda.go
index db40589..c8631a5 100644
--- a/gwda.go
+++ b/gwda.go
@@ -68,7 +68,12 @@ func executeHTTP(method string, rawURL string, rawBody []byte, httpCli *http.Cli
 	}()
 
 	rawResp, err = ioutil.ReadAll(resp.Body)
-	debugLog(fmt.Sprintf("<-- %s %s %d %s\n%s\n", method, rawURL, resp.StatusCode, time.Since(start), rawResp))
+	respBody := fmt.Sprintf("<-- %s %s %d %s", method, rawURL, resp.StatusCode, time.Since(start))
+	if !strings.HasSuffix(rawURL, "screenshot") {
+		// avoid printing screenshot data
+		respBody += fmt.Sprintf("\n%s", rawResp)
+	}
+	debugLog(respBody)
 	if err != nil {
 		return nil, err
 	}
@@ -606,6 +611,7 @@ func elementIDFromValue(val map[string]string) string {
 	return ""
 }
 
+// performance ranking: class name > accessibility id > link text > predicate > class chain > xpath
 type BySelector struct {
 	ClassName ElementType `json:"class name"`
 
@@ -624,7 +630,7 @@ type BySelector struct {
 
 	ClassChain string `json:"class chain"`
 
-	XPath string `json:"xpath"`
+	XPath string `json:"xpath"` // not recommended, it's slow because it is not supported by XCTest natively
 }
 
 func (wl BySelector) getUsingAndValue() (using, value string) {
@@ -879,8 +885,8 @@ const (
 )
 
 type Point struct {
-	X int `json:"x"`
-	Y int `json:"y"`
+	X int `json:"x"` // upper left X coordinate of selected element
+	Y int `json:"y"` // upper left Y coordinate of selected element
 }
 
 type Rect struct {
@@ -888,6 +894,26 @@ type Rect struct {
 	Size
 }
 
+type DataOption func(data map[string]interface{})
+
+func WithCustomOption(key string, value interface{}) DataOption {
+	return func(data map[string]interface{}) {
+		data[key] = value
+	}
+}
+
+func WithPressDuration(duraion float64) DataOption {
+	return func(data map[string]interface{}) {
+		data["duration"] = duraion
+	}
+}
+
+func WithFrequency(frequency int) DataOption {
+	return func(data map[string]interface{}) {
+		data["frequency"] = frequency
+	}
+}
+
 // WebDriver defines methods supported by WebDriver drivers.
 type WebDriver interface {
 	// NewSession starts a new session and returns the SessionInfo.
@@ -970,8 +996,8 @@ type WebDriver interface {
 	AppAuthReset(ProtectedResource) error
 
 	// Tap Sends a tap event at the coordinate.
-	Tap(x, y int) error
-	TapFloat(x, y float64) error
+	Tap(x, y int, options ...DataOption) error
+	TapFloat(x, y float64, options ...DataOption) error
 
 	// DoubleTap Sends a double tap event at the coordinate.
 	DoubleTap(x, y int) error
@@ -983,13 +1009,13 @@ type WebDriver interface {
 	TouchAndHoldFloat(x, y float64, second ...float64) error
 
 	// Drag Initiates a press-and-hold gesture at the coordinate, then drags to another coordinate.
-	//  pressForDuration: The default value is 1 second.
-	Drag(fromX, fromY, toX, toY int, pressForDuration ...float64) error
-	DragFloat(fromX, fromY, toX, toY float64, pressForDuration ...float64) error
+	// WithPressDuration option can be used to set pressForDuration (default to 1 second).
+	Drag(fromX, fromY, toX, toY int, options ...DataOption) error
+	DragFloat(fromX, fromY, toX, toY float64, options ...DataOption) error
 
 	// Swipe works like Drag, but `pressForDuration` value is 0
-	Swipe(fromX, fromY, toX, toY int) error
-	SwipeFloat(fromX, fromY, toX, toY float64) error
+	Swipe(fromX, fromY, toX, toY int, options ...DataOption) error
+	SwipeFloat(fromX, fromY, toX, toY float64, options ...DataOption) error
 
 	ForceTouch(x, y int, pressure float64, second ...float64) error
 	ForceTouchFloat(x, y, pressure float64, second ...float64) error
@@ -1006,8 +1032,8 @@ type WebDriver interface {
 
 	// SendKeys Types a string into active element. There must be element with keyboard focus,
 	// otherwise an error is raised.
-	//  frequency: Frequency of typing (letters per sec). The default value is 60
-	SendKeys(text string, frequency ...int) error
+	// WithFrequency option can be used to set frequency of typing (letters per sec). The default value is 60
+	SendKeys(text string, options ...DataOption) error
 
 	// KeyboardDismiss Tries to dismiss the on-screen keyboard
 	KeyboardDismiss(keyNames ...string) error