diff --git a/modules/dns/main.tf b/modules/dns/main.tf
index 19c2d0d7..7e6154a2 100644
--- a/modules/dns/main.tf
+++ b/modules/dns/main.tf
@@ -22,10 +22,10 @@ locals {
   zone = (
     var.zone_create
     ? try(
-    	google_dns_managed_zone.non-public.0, try(
-      	  google_dns_managed_zone.public.0, null
-    	)
+      google_dns_managed_zone.non-public.0, try(
+        google_dns_managed_zone.public.0, null
       )
+    )
     : try(data.google_dns_managed_zone.public.0, null)
   )
   dns_keys = try(
@@ -94,12 +94,12 @@ resource "google_dns_managed_zone" "non-public" {
 }
 
 data "google_dns_managed_zone" "public" {
-  count      = var.zone_create ? 0 : 1
-  name = var.name
+  count = var.zone_create ? 0 : 1
+  name  = var.name
 }
 
 resource "google_dns_managed_zone" "public" {
-  count      = (var.zone_create && var.type == "public" ) ? 1 : 0
+  count       = (var.zone_create && var.type == "public") ? 1 : 0
   project     = var.project_id
   name        = var.name
   dns_name    = var.domain
@@ -132,7 +132,7 @@ resource "google_dns_managed_zone" "public" {
 }
 
 data "google_dns_keys" "dns_keys" {
-  count        = var.zone_create && ( var.dnssec_config == {} || var.type != "public" ) ? 0 : 1
+  count        = var.zone_create && (var.dnssec_config == {} || var.type != "public") ? 0 : 1
   managed_zone = local.zone.id
 }
 
diff --git a/modules/dns/variables.tf b/modules/dns/variables.tf
index d6e267d9..be32349b 100644
--- a/modules/dns/variables.tf
+++ b/modules/dns/variables.tf
@@ -97,6 +97,10 @@ variable "type" {
   description = "Type of zone to create, valid values are 'public', 'private', 'forwarding', 'peering', 'service-directory'."
   type        = string
   default     = "private"
+  validation {
+    condition     = contains(["public", "private", "forwarding", "peering", "service-directory"], var.type)
+    error_message = "Zone must be one of 'public', 'private', 'forwarding', 'peering', 'service-directory'."
+  }
 }
 
 variable "zone_create" {
@@ -106,3 +110,4 @@ variable "zone_create" {
 }
 
 
+
diff --git a/modules/gcs/variables.tf b/modules/gcs/variables.tf
index 3f48caa6..7c8d800f 100644
--- a/modules/gcs/variables.tf
+++ b/modules/gcs/variables.tf
@@ -88,6 +88,10 @@ variable "storage_class" {
   description = "Bucket storage class."
   type        = string
   default     = "MULTI_REGIONAL"
+  validation {
+    condition     = contains(["STANDARD", "MULTI_REGIONAL", "REGIONAL", "NEARLINE", "COLDLINE", "ARCHIVE"], var.storage_class)
+    error_message = "Storage class must be one of STANDARD, MULTI_REGIONAL, REGIONAL, NEARLINE, COLDLINE, ARCHIVE."
+  }
 }
 
 variable "versioning" {
diff --git a/modules/net-vpc/variables.tf b/modules/net-vpc/variables.tf
index 7aa0fd8b..6c3ab855 100644
--- a/modules/net-vpc/variables.tf
+++ b/modules/net-vpc/variables.tf
@@ -100,6 +100,11 @@ variable "routing_mode" {
   description = "The network routing mode (default 'GLOBAL')"
   type        = string
   default     = "GLOBAL"
+  validation {
+    condition     = var.routing_mode == "GLOBAL" || var.routing_mode == "REGIONAL"
+    error_message = "Routing type must be GLOBAL or REGIONAL."
+  }
+
 }
 
 variable "shared_vpc_host" {
diff --git a/modules/project/variables.tf b/modules/project/variables.tf
index a0e965bf..8972166a 100644
--- a/modules/project/variables.tf
+++ b/modules/project/variables.tf
@@ -83,6 +83,10 @@ variable "parent" {
   description = "Parent folder or organization in 'folders/folder_id' or 'organizations/org_id' format."
   type        = string
   default     = null
+  validation {
+    condition     = can(regex("(organizations|folders)/[0-9]+", var.parent))
+    error_message = "Parent must be of the form folders/folder_id or organizations/organization_id."
+  }
 }
 
 variable "policy_boolean" {