diff --git a/variables.tf b/variables.tf
index 9d86f38..f6934a0 100644
--- a/variables.tf
+++ b/variables.tf
@@ -1,7 +1,14 @@
-variable "project_id" {}
+variable "project_id" {
+  type        = string
+  description = "The ID of the project to deploy resources into"
+}
+
 variable "region" {
-  default = "us-central1"
+  type        = string
+  description = "The region to deploy resources into"
 }
-variable "zone" {
-  default = "us-central1-f"
+
+variable "network_cidr" {
+  type        = string
+  description = "The CIDR block for the VPC network"
 }