What argument is required when declaring a Terraform output?

When declaring an output in Terraform, the required argument is the value. The value argument is the primary component that specifies what data you want to extract from your Terraform configuration and display as an output after execution. This value can be derived from various resources or attributes in your configuration. By including this argument, you ensure that the necessary information is captured and made available after provisioning your resources.

While there are additional optional arguments like description, format, or secure that can enhance the output declaration, they are not mandatory. The description argument allows users to provide helpful context or information about the output, format offers options on how the output is displayed, and secure specifies whether or not to mask the output in the command line interface. However, without the value argument, the output would lack the actual content to inform users about the state of the infrastructure, thus making it a crucial component in output declarations.