TerraCurl is a utility Terraform provider that enables engineers to make managed and unmanaged API calls in their Terraform code, allowing them to work around unsupported resources in Terraform providers. It provides instructions for creating and deleting resources, as well as reading data from responses and handling errors with retry logic. The provider can be used in both managed and unmanaged API calls, and it supports authenticated and mutually authenticated calls with TLS. With its flexible design, TerraCurl opens up new possibilities and use cases in workflows, making it a valuable tool for engineers working with Terraform.