diff --git a/internal/hbooking/handlers/create_booking.go b/internal/hbooking/handlers/create_booking.go
index 4b13977..773975b 100644
--- a/internal/hbooking/handlers/create_booking.go
+++ b/internal/hbooking/handlers/create_booking.go
@@ -1,8 +1,9 @@
 package handlers
 
 import (
+	"context"
 	"errors"
-	"net/http"
+	"fmt"
 	"strconv"
 	"time"
 
@@ -11,7 +12,7 @@ import (
 	"github.com/spatecon/hbooking/internal/hbooking/domain"
 )
 
-type Booking struct {
+type CreateBookingResponse struct {
 	ID             string `json:"id,omitempty"`
 	WorkshopID     int64  `json:"workshop_id"`
 	ClientID       string `json:"client_id"`
@@ -21,95 +22,120 @@ type Booking struct {
 }
 
 type CreateBookingRequest struct {
-	Booking
+	WorkshopID     int64  `json:"workshop_id"`
+	ClientID       string `json:"client_id"`
+	BeginAt        string `json:"begin_at"`
+	EndAt          string `json:"end_at"`
+	ClientTimezone string `json:"client_timezone"`
 }
 
 func (h *Handlers) CreateBooking(c *gin.Context) {
 	var req CreateBookingRequest
-	err := c.ShouldBindJSON(&req)
-	if BadRequest(c, err, "failed to bind request") {
+	if BadRequest(c, makeCreateBookingRequest(c, &req)) {
 		return
 	}
 
-	workshopID, err := strconv.ParseInt(c.Param("workshop_id"), 10, 64)
-	if BadRequest(c, err, "failed to parse workshop_id") {
+	var booking domain.Booking
+	if BadRequest(c, requestToDomainBooking(&req, &booking)) {
 		return
 	}
 
-	booking := &domain.Booking{
-		WorkshopID: workshopID,
-		ClientID:   req.ClientID,
-	}
+	b, err := createBookingService(c.Request.Context(), h.repo, &booking)
+	if err != nil {
+		if ValidationFailed(c, err) {
+			return
+		}
 
-	booking.ClientTimezone, err = time.LoadLocation(req.ClientTimezone)
-	if BadRequest(c, err, "failed to load client timezone") {
+		InternalServerError(c, err)
 		return
 	}
 
+	c.JSON(200, makeCreateBookingResponse(b))
+}
+
+func makeCreateBookingRequest(c *gin.Context, r *CreateBookingRequest) error {
+	var err error
+	if err = c.ShouldBindJSON(r); err != nil {
+		return fmt.Errorf("failed to bind request: %w", err)
+	}
+
+	if r.WorkshopID, err = strconv.ParseInt(c.Param("workshop_id"), 10, 64); err != nil {
+		return fmt.Errorf("failed to parse workshop_id")
+	}
+
+	return nil
+}
+
+func requestToDomainBooking(req *CreateBookingRequest, booking *domain.Booking) error {
+	clientTimezone, err := time.LoadLocation(req.ClientTimezone)
+	if err != nil {
+		return fmt.Errorf("failed to load client timezone")
+	}
+
 	beginAt, err := time.Parse("02-01-2006 15:04", req.BeginAt)
-	if BadRequest(c, err, "failed to parse begin_at") {
-		return
+	if err != nil {
+		return fmt.Errorf("failed to parse begin_at")
 	}
 
 	endAt, err := time.Parse("02-01-2006 15:04", req.EndAt)
-	if BadRequest(c, err, "failed to parse end_at") {
-		return
+	if err != nil {
+		return fmt.Errorf("failed to parse end_at")
 	}
 
+	booking.WorkshopID = req.WorkshopID
+	booking.ClientID = req.ClientID
 	booking.BeginAt = time.Date(
 		beginAt.Year(),
 		beginAt.Month(),
 		beginAt.Day(),
 		beginAt.Hour(), beginAt.Minute(), 0, 0,
-		booking.ClientTimezone,
-	).In(booking.ClientTimezone)
-
+		clientTimezone,
+	).In(clientTimezone)
 	booking.EndAt = time.Date(
 		endAt.Year(),
 		endAt.Month(),
 		endAt.Day(),
 		endAt.Hour(), endAt.Minute(), 0, 0,
-		booking.ClientTimezone,
-	).In(booking.ClientTimezone)
+		clientTimezone,
+	).In(clientTimezone)
+	booking.ClientTimezone = clientTimezone
+
+	return nil
+}
 
+func createBookingService(ctx context.Context, repo Repository, booking *domain.Booking) (*domain.Booking, error) {
 	now := time.Now().In(booking.ClientTimezone)
-	if ValidationFailed(c, booking.BeginAt.Before(now), "begin_at is in the past") {
-		return
+	if booking.BeginAt.Before(now) {
+		return nil, ValidationErrorStr("begin_at is in the past")
 	}
 
-	if ValidationFailed(c, booking.EndAt.Before(booking.BeginAt), "end_at is before begin_at") {
-		return
+	if booking.EndAt.Before(booking.BeginAt) {
+		return nil, ValidationErrorStr("end_at is before begin_at")
 	}
 
 	duration := booking.EndAt.Sub(booking.BeginAt)
-	if ValidationFailed(c,
-		duration < minBookingDuration || duration > maxBookingDuration,
-		"invalid booking duration: must be in range [30m, 4h]",
-	) {
-		return
+	if duration < minBookingDuration || duration > maxBookingDuration {
+		return nil, ValidationErrorStr("invalid booking duration: must be in range [30m, 4h]")
 	}
 
-	booking, err = h.repo.CreateBooking(c.Request.Context(), booking)
+	b, err := repo.CreateBooking(ctx, booking)
 	if err != nil {
-		if errors.Is(err, domain.ErrBookingOverlap) {
-			Error(c, err, http.StatusBadRequest)
-			return
-		}
-		if errors.Is(err, domain.ErrBookingOutOfWorkshopSchedule) {
-			Error(c, err, http.StatusBadRequest)
-			return
+		if errors.Is(err, domain.ErrBookingOverlap) || errors.Is(err, domain.ErrBookingOutOfWorkshopSchedule) {
+			return nil, ValidationError(err)
 		}
 
-		Error(c, err, http.StatusInternalServerError)
-		return
+		return nil, err
 	}
+	return b, nil
+}
 
-	c.JSON(200, Booking{
-		ID:             booking.ID.String(),
-		WorkshopID:     booking.WorkshopID,
-		ClientID:       booking.ClientID,
-		BeginAt:        booking.BeginAt.Format("02-01-2006 15:04"),
-		EndAt:          booking.EndAt.Format("02-01-2006 15:04"),
-		ClientTimezone: booking.ClientTimezone.String(),
-	})
+func makeCreateBookingResponse(b *domain.Booking) CreateBookingResponse {
+	return CreateBookingResponse{
+		ID:             b.ID.String(),
+		WorkshopID:     b.WorkshopID,
+		ClientID:       b.ClientID,
+		BeginAt:        b.BeginAt.Format("02-01-2006 15:04"),
+		EndAt:          b.EndAt.Format("02-01-2006 15:04"),
+		ClientTimezone: b.ClientTimezone.String(),
+	}
 }
diff --git a/internal/hbooking/handlers/error.go b/internal/hbooking/handlers/error.go
index 2c50874..a0caf67 100644
--- a/internal/hbooking/handlers/error.go
+++ b/internal/hbooking/handlers/error.go
@@ -11,22 +11,51 @@ type ErrorResponse struct {
 	Error string `json:"error"`
 }
 
-func ValidationFailed(c *gin.Context, cond bool, description string) bool {
-	if !cond {
+type serviceError struct {
+	err error
+	msg string
+}
+
+func (e serviceError) Error() string {
+	return e.msg
+}
+
+func (e serviceError) Unwrap() error {
+	return e.err
+}
+
+func ValidationError(err error) serviceError {
+	return serviceError{msg: "validation failed: " + err.Error(), err: err}
+}
+
+func ValidationErrorStr(err string) serviceError {
+	return ValidationError(fmt.Errorf(err))
+}
+
+func ValidationFailed(c *gin.Context, err error) bool {
+	if err == nil {
+		return false
+	}
+
+	if _, ok := err.(serviceError); !ok {
 		return false
 	}
 
-	err := fmt.Errorf("validation failed: %s", description)
 	return Error(c, err, http.StatusUnprocessableEntity)
 }
 
-func BadRequest(c *gin.Context, err error, description string) bool {
+func BadRequest(c *gin.Context, err error) bool {
+	return Error(c, err, http.StatusBadRequest)
+}
+
+func InternalServerError(c *gin.Context, err error) bool {
 	if err == nil {
 		return false
 	}
 
-	err = fmt.Errorf("%s: %w", description, err)
-	return Error(c, err, http.StatusBadRequest)
+	_ = c.Error(err)
+	c.Status(http.StatusInternalServerError)
+	return true
 }
 
 func Error(c *gin.Context, err error, code int) bool {
diff --git a/internal/hbooking/handlers/list.go b/internal/hbooking/handlers/list.go
deleted file mode 100644
index 7daa161..0000000
--- a/internal/hbooking/handlers/list.go
+++ /dev/null
@@ -1,42 +0,0 @@
-package handlers
-
-import (
-	"net/http"
-	"strconv"
-
-	"github.com/gin-gonic/gin"
-)
-
-type ListBookingsRequest struct {
-	WorkshopID int `json:"workshop_id"`
-}
-
-type ListBookingsResponse struct {
-	Bookings []*Booking `json:"bookings"`
-}
-
-func (h *Handlers) ListBookings(c *gin.Context) {
-	workshopID, err := strconv.ParseInt(c.Param("workshop_id"), 10, 64)
-	if BadRequest(c, err, "failed to parse workshop_id") {
-		return
-	}
-
-	bookings, err := h.repo.ListBookings(c.Request.Context(), workshopID)
-	if Error(c, err, http.StatusInternalServerError) {
-		return
-	}
-
-	respBookings := make([]*Booking, 0, len(bookings))
-	for _, b := range bookings {
-		respBookings = append(respBookings, &Booking{
-			WorkshopID:     b.WorkshopID,
-			ClientID:       b.ClientID,
-			BeginAt:        b.BeginAt.Format("02-01-2006 15:04"),
-			EndAt:          b.EndAt.Format("02-01-2006 15:04"),
-			ClientTimezone: b.ClientTimezone.String(),
-		})
-	}
-
-	c.JSON(200, ListBookingsResponse{Bookings: respBookings})
-
-}
diff --git a/internal/hbooking/handlers/list_booking.go b/internal/hbooking/handlers/list_booking.go
new file mode 100644
index 0000000..c41fa23
--- /dev/null
+++ b/internal/hbooking/handlers/list_booking.go
@@ -0,0 +1,64 @@
+package handlers
+
+import (
+	"fmt"
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+
+	"github.com/spatecon/hbooking/internal/hbooking/domain"
+)
+
+type ListBookingsRequest struct {
+	WorkshopID int64 `json:"workshop_id"`
+}
+
+type ListBookingsResponse struct {
+	Bookings []ListBookingResponse `json:"bookings"`
+}
+
+type ListBookingResponse struct {
+	WorkshopID     int64  `json:"workshop_id"`
+	ClientID       string `json:"client_id"`
+	BeginAt        string `json:"begin_at"`
+	EndAt          string `json:"end_at"`
+	ClientTimezone string `json:"client_timezone"`
+}
+
+func (h *Handlers) ListBookings(c *gin.Context) {
+	var req ListBookingsRequest
+	if BadRequest(c, makeListBookingsRequest(c, &req)) {
+		return
+	}
+
+	bookings, err := h.repo.ListBookings(c.Request.Context(), req.WorkshopID)
+	if InternalServerError(c, err) {
+		return
+	}
+
+	c.JSON(200, makeListBookingsResponse(bookings))
+
+}
+
+func makeListBookingsRequest(c *gin.Context, r *ListBookingsRequest) error {
+	var err error
+	if r.WorkshopID, err = strconv.ParseInt(c.Param("workshop_id"), 10, 64); err != nil {
+		return fmt.Errorf("failed to parse workshop_id")
+	}
+
+	return nil
+}
+
+func makeListBookingsResponse(bookings []*domain.Booking) ListBookingsResponse {
+	respBookings := make([]ListBookingResponse, len(bookings))
+	for i, b := range bookings {
+		respBookings[i] = ListBookingResponse{
+			WorkshopID:     b.WorkshopID,
+			ClientID:       b.ClientID,
+			BeginAt:        b.BeginAt.Format("02-01-2006 15:04"),
+			EndAt:          b.EndAt.Format("02-01-2006 15:04"),
+			ClientTimezone: b.ClientTimezone.String(),
+		}
+	}
+	return ListBookingsResponse{Bookings: respBookings}
+}