diff --git a/internal/model/host.go b/internal/model/host.go
index 626f222..27c39fc 100644
--- a/internal/model/host.go
+++ b/internal/model/host.go
@@ -1,6 +1,7 @@
 package model
 
 import (
+	"fmt"
 	"go.mongodb.org/mongo-driver/bson/primitive"
 	"time"
 )
@@ -21,3 +22,17 @@ type HostRequest struct {
 	Host  string `json:"host"`
 	Stage string `json:"stage"`
 }
+
+func (h *Host) String() string {
+	return fmt.Sprintf(
+		fmt.Sprintf("Id: %s", h.Id.String()),
+		fmt.Sprintf("ProjectId: %s", h.ProjectId),
+		fmt.Sprintf("Host: %s", h.Host),
+		fmt.Sprintf("Stage: %s", h.Stage),
+		fmt.Sprintf("Verified: %s", h.VerifyToken),
+		fmt.Sprintf("VerifyToken: %s", h.VerifyToken),
+		fmt.Sprintf("UpdatedAt: %s", h.UpdatedAt),
+		fmt.Sprintf("CreatedAt: %s", h.CreatedAt),
+		fmt.Sprintf("DeletedAt: %s", h.DeletedAt),
+	)
+}
diff --git a/internal/service/domain_notification.go b/internal/service/domain_notification.go
index ff7977e..77e722d 100644
--- a/internal/service/domain_notification.go
+++ b/internal/service/domain_notification.go
@@ -20,31 +20,43 @@ const (
 func (c *Client) SendNotification(host string, notification model.Notification) (*model.SuccessMessage, error) {
 	err := validateNotificationRequest(notification)
 	if err != nil {
+		log.Debug("notification-request-validation is failed; ", err.Error())
 		return nil, err
 	}
 
 	validatedHost, err := url.Parse(host)
 	if err != nil {
+		log.Debug("parse host is failed; ", err.Error())
 		return nil, fmt.Errorf("failed to parse host")
 	}
 
 	hosts, err := c.db.ListHosts(model.Host{ProjectId: notification.ProjectId})
 	if err != nil {
 		log.Error(err)
+		log.Debug("failed to list hosts; ", err.Error())
 		return nil, fmt.Errorf("failed to verify host")
 	}
 
 	if index := ifHostInHosts(validatedHost.Host, hosts); hosts == nil || index == -1 || !hosts[index].Verified {
+		log.Debug(
+			"failed to verify hosts; ",
+			fmt.Sprintf("host: %s; ", validatedHost.Host),
+			fmt.Sprintf("index: %d; ", index),
+			fmt.Sprintf("length: %d; ", len(hosts)),
+			fmt.Sprintf("hosts: %v", hosts),
+		)
 		return nil, fmt.Errorf("failed to verify host")
 	}
 
 	flows, err := c.db.ListFlows(model.Flow{ProjectId: notification.ProjectId})
 	if err != nil {
 		log.Error(err)
+		log.Debug("failed to list flows; ", err.Error())
 		return nil, fmt.Errorf("failed to list flows")
 	}
 
 	if flows == nil || len(flows) == 0 {
+		log.Debug("failed to list flows; ", "there are no flows; ", flows)
 		return nil, fmt.Errorf("failed to list flows")
 	}