diff --git a/action_create.go b/action_create.go
index 8b23c5b..2781186 100644
--- a/action_create.go
+++ b/action_create.go
@@ -3,31 +3,38 @@ package devicemngmt
 import (
 	"context"
 	"errors"
+	"fmt"
 
 	"github.com/Selly-Modules/logger"
 	"github.com/Selly-Modules/mongodb"
-	ua "github.com/mssola/user_agent"
 	"go.mongodb.org/mongo-driver/bson"
 )
 
-// DeviceCreate ...
-type DeviceCreate struct {
+// CreateOptions ...
+type CreateOptions struct {
 	DeviceID   string
 	UserID     string
 	UserAgent  string
 	AppVersion string
 	IP         string
 	FCMToken   string
+	AuthToken  string
 	Language   string
 }
 
 // Create ...
-func (s Service) Create(payload DeviceCreate) error {
+func (s Service) Create(payload CreateOptions) error {
 	var (
 		col = s.getDeviceCollection()
 		ctx = context.Background()
 	)
 
+	// Validate payload
+	err := payload.validate()
+	if err != nil {
+		return err
+	}
+
 	// New device data from payload
 	deviceData, err := payload.newDevice()
 	if err != nil {
@@ -43,7 +50,7 @@ func (s Service) Create(payload DeviceCreate) error {
 		})
 	}
 	if !device.ID.IsZero() {
-		return errors.New("deviceID already exists")
+		return errors.New("this device is already existed")
 	}
 
 	// Create device
@@ -53,78 +60,33 @@ func (s Service) Create(payload DeviceCreate) error {
 			"doc": deviceData,
 			"err": err.Error(),
 		})
-		return errors.New("create device fail")
+		return fmt.Errorf("error when create device: %s", err.Error())
 	}
 
 	return nil
 }
 
-func (payload DeviceCreate) newDevice() (result Device, err error) {
+func (payload CreateOptions) newDevice() (result Device, err error) {
 	timeNow := now()
 	device := Device{
 		ID:             mongodb.NewObjectID(),
+		DeviceID:       payload.DeviceID,
+		OSName:         getOSName(payload.UserAgent),
+		OSVersion:      getOSVersion(payload.UserAgent),
+		IP:             payload.IP,
+		Language:       getLanguage(payload.Language),
+		AuthToken:      payload.AuthToken,
 		LastActivityAt: timeNow,
 		CreatedAt:      timeNow,
 		FCMToken:       payload.FCMToken,
 	}
 
-	// Set deviceID
-	if payload.DeviceID == "" {
-		logger.Error("devicemngt - Create: no deviceID data", logger.LogData{
-			"payload": payload,
-		})
-		err = errors.New("no deviceID data")
-		return
-	}
-	device.DeviceID = payload.DeviceID
-
-	// 	OSName, OSVersion
-	if payload.UserAgent == "" {
-		logger.Error("devicemngt - Create: no userAgent data", logger.LogData{
-			"payload": payload,
-		})
-		err = errors.New("no userAgent data")
-		return
-	}
-	uaData := ua.New(payload.UserAgent)
-	device.OSName = uaData.OSInfo().Name
-	device.OSVersion = uaData.OSInfo().Version
-
 	// App version
 	if payload.AppVersion != "" {
 		device.AppVersion = payload.AppVersion
 		device.IsMobile = true
 	}
 
-	// IP
-	if payload.IP == "" {
-		logger.Error("devicemngt - Create: no ip data", logger.LogData{
-			"payload": payload,
-		})
-		err = errors.New("no ip data")
-		return
-	}
-
-	// Language, default is vietnamese(vi)
-	if payload.Language == "" {
-		device.Language = viLanguage
-	} else {
-		device.Language = enLanguage
-	}
-
-	// userIDe
-	userID, _ := mongodb.NewIDFromString(payload.UserID)
-	if userID.IsZero() {
-		logger.Error("devicemngt - Create: invalid userID data", logger.LogData{
-			"payload": payload,
-		})
-		err = errors.New("invalid userID data")
-		return
-	}
-
-	// Generate authToken from userID
-	device.AuthToken = s.generateAuthToken(userID)
-
 	result = device
 	return
 }
diff --git a/auth_token.go b/auth_token.go
deleted file mode 100644
index 88c7ddd..0000000
--- a/auth_token.go
+++ /dev/null
@@ -1,17 +0,0 @@
-package devicemngmt
-
-import (
-	"time"
-
-	"github.com/dgrijalva/jwt-go"
-	"go.mongodb.org/mongo-driver/bson/primitive"
-)
-
-func (s Service) generateAuthToken(userID primitive.ObjectID) string {
-	token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
-		"_id": userID,
-		"exp": now().Add(time.Second * 15552000).Unix(), // 6 months
-	})
-	tokenString, _ := token.SignedString([]byte(s.AuthSecret))
-	return tokenString
-}
diff --git a/constant.go b/constant.go
index a6e1949..ca4c13f 100644
--- a/constant.go
+++ b/constant.go
@@ -2,10 +2,10 @@ package devicemngmt
 
 // Constant ...
 const (
-	TableDevice = "devices"
+	tableDevice = "devices"
 
 	timezoneHCM = "Asia/Ho_Chi_Minh"
 
-	viLanguage = "vi"
-	enLanguage = "en"
+	langVi = "vi"
+	langEn = "en"
 )
diff --git a/devicemngt.go b/devicemngt.go
index 3574ec1..cc2b7e7 100644
--- a/devicemngt.go
+++ b/devicemngt.go
@@ -19,8 +19,6 @@ type Config struct {
 	MongoDB MongoDBConfig
 	// Table prefix, each service has its own prefix
 	TablePrefix string
-	// Auth secret, used to sign token
-	AuthSecret string
 }
 
 // Service ...
@@ -32,9 +30,9 @@ type Service struct {
 var s *Service
 
 // Init ...
-func Init(config Config) error {
-	if config.MongoDB.Host == "" || config.TablePrefix == "" || config.AuthSecret == "" {
-		return errors.New("please provide all necessary information for init device")
+func Init(config Config) (*Service, error) {
+	if config.MongoDB.Host == "" || config.TablePrefix == "" {
+		return nil, errors.New("please provide all necessary information for init device")
 	}
 
 	// Connect MongoDB
@@ -48,7 +46,7 @@ func Init(config Config) error {
 	)
 	if err != nil {
 		fmt.Println("Cannot init module DEVICE MANAGEMENT", err)
-		return err
+		return nil, err
 	}
 
 	s = &Service{
@@ -56,7 +54,7 @@ func Init(config Config) error {
 		DB:     db,
 	}
 
-	return nil
+	return s, nil
 }
 
 // GetInstance ...
diff --git a/helper.go b/helper.go
index 9b7a54f..3c1d026 100644
--- a/helper.go
+++ b/helper.go
@@ -3,10 +3,29 @@ package devicemngmt
 import (
 	"fmt"
 
+	ua "github.com/mssola/user_agent"
 	"go.mongodb.org/mongo-driver/mongo"
 )
 
 //  getDeviceCollection ...
 func (s Service) getDeviceCollection() *mongo.Collection {
-	return s.DB.Collection(fmt.Sprintf("%s-%s", s.TablePrefix, TableDevice))
+	return s.DB.Collection(fmt.Sprintf("%s-%s", s.TablePrefix, tableDevice))
+}
+
+func getOSName(userAgent string) string {
+	uaData := ua.New(userAgent)
+	return uaData.OSInfo().Name
+}
+
+func getOSVersion(userAgent string) string {
+	uaData := ua.New(userAgent)
+	return uaData.OSInfo().Version
+}
+
+func getLanguage(lang string) string {
+	// Language, default is vietnamese(vi)
+	if lang == langEn {
+		return langEn
+	}
+	return langVi
 }
diff --git a/model.go b/model.go
index bd684f3..22a2796 100644
--- a/model.go
+++ b/model.go
@@ -8,17 +8,17 @@ import (
 
 // Device ...
 type Device struct {
-	ID             primitive.ObjectID `bson:"_id"`
-	DeviceID       string             `bson:"deviceID"` // unique
-	IP             string             `bson:"ip"`
-	OSName         string             `bson:"osName"`
-	OSVersion      string             `bson:"osVersion"`
-	AppVersion     string             `bson:"appVersion"`
-	Language       string             `bson:"language"` // vi, en
-	IsMobile       bool               `bson:"isMobile"`
-	LastActivityAt time.Time          `bson:"lastActivityAt"`
-	UserID         primitive.ObjectID `bson:"userID"`
-	AuthToken      string             `bson:"authToken"`
-	FCMToken       string             `bson:"fcmToken"`
-	CreatedAt      time.Time          `bson:"createdAt"`
+	ID             primitive.ObjectID `bson:"_id" json:"_id"`
+	DeviceID       string             `bson:"deviceID" json:"deviceID"` // unique
+	IP             string             `bson:"ip" json:"ip"`
+	OSName         string             `bson:"osName" json:"osName"`
+	OSVersion      string             `bson:"osVersion" json:"osVersion"`
+	AppVersion     string             `bson:"appVersion" json:"appVersion"`
+	Language       string             `bson:"language" json:"language"` // vi, en
+	IsMobile       bool               `bson:"isMobile" json:"isMobile"`
+	LastActivityAt time.Time          `bson:"lastActivityAt" json:"lastActivityAt"`
+	UserID         primitive.ObjectID `bson:"userID" json:"userID"`
+	AuthToken      string             `bson:"authToken" json:"authToken"`
+	FCMToken       string             `bson:"fcmToken" json:"fcmToken"`
+	CreatedAt      time.Time          `bson:"createdAt" json:"createdAt"`
 }
diff --git a/validate.go b/validate.go
new file mode 100644
index 0000000..9efc49f
--- /dev/null
+++ b/validate.go
@@ -0,0 +1,51 @@
+package devicemngmt
+
+import (
+	"errors"
+
+	"github.com/Selly-Modules/logger"
+)
+
+func (co CreateOptions) validate() error{
+	// DeviceID
+	if co.DeviceID == "" {
+		logger.Error("devicemngt - Create: no deviceID data", logger.LogData{
+			"payload": co,
+		})
+		return errors.New("no deviceID data")
+	}
+
+	// UserAgent
+	if co.UserAgent == "" {
+		logger.Error("devicemngt - Create: no userAgent data", logger.LogData{
+			"payload": co,
+		})
+		return  errors.New("no userAgent data")
+	}
+
+	// IP
+	if co.IP == "" {
+		logger.Error("devicemngt - Create: no ip data", logger.LogData{
+			"payload": co,
+		})
+		return errors.New("no ip data")
+	}
+
+	// UserID
+	if co.UserID == "" {
+		logger.Error("devicemngt - Create: no userID data", logger.LogData{
+			"payload": co,
+		})
+		return errors.New("no userID data")
+	}
+
+	// AuthToken
+	if co.AuthToken == "" {
+		logger.Error("devicemngt - Create: no authToken data", logger.LogData{
+			"payload": co,
+		})
+		return errors.New("no authToken data")
+	}
+
+	return nil
+}