You can specify the type of a variable to enforce that the provided value matches the expected type.

variable "vpc_cidr_block" {
  description = "CIDR block for the VPC"
  type        = string
}
 
variable "availability_zones" {
  description = "List of availability zones"
  type        = list(string)
}
 
variable "instance_tags" {
  description = "Map of tags to assign to the instance"
  type        = map(string)
}