diff --git a/pkg/errs/errno.go b/pkg/errs/errno.go
index 8cd3743fe1b..b8a882cd187 100644
--- a/pkg/errs/errno.go
+++ b/pkg/errs/errno.go
@@ -160,7 +160,7 @@ var (
 	ErrLoadRuleGroup     = errors.Normalize("load rule group failed", errors.RFCCodeText("PD:placement:ErrLoadRuleGroup"))
 	ErrBuildRuleList     = errors.Normalize("build rule list failed, %s", errors.RFCCodeText("PD:placement:ErrBuildRuleList"))
 	ErrPlacementDisabled = errors.Normalize("placement rules feature is disabled", errors.RFCCodeText("PD:placement:ErrPlacementDisabled"))
-	ErrKeyFormat         = errors.Normalize("key should be in hex format", errors.RFCCodeText("PD:placement:ErrKeyFormat"))
+	ErrKeyFormat         = errors.Normalize("key should be in hex format, %s", errors.RFCCodeText("PD:placement:ErrKeyFormat"))
 	ErrRuleNotFound      = errors.Normalize("rule not found", errors.RFCCodeText("PD:placement:ErrRuleNotFound"))
 )
 
diff --git a/server/api/rule.go b/server/api/rule.go
index 116a50f6259..77aad42eb42 100644
--- a/server/api/rule.go
+++ b/server/api/rule.go
@@ -208,7 +208,7 @@ func (h *ruleHandler) GetRulesByKey(w http.ResponseWriter, r *http.Request) {
 	keyHex := mux.Vars(r)["key"]
 	key, err := hex.DecodeString(keyHex)
 	if err != nil {
-		h.rd.JSON(w, http.StatusBadRequest, errs.ErrKeyFormat.Error())
+		h.rd.JSON(w, http.StatusBadRequest, errs.ErrKeyFormat.FastGenByArgs(err).Error())
 		return
 	}
 	rules := manager.GetRulesByKey(key)