I am in the process of writing documentation for a software project. I would like to understand what would be the best tense to use for the description of the code/tools that had been (?) developed by the time I started writing the document.
For example, consider the following sentence:
This document describes the programming conventions used in the library development, the library directory structure and the supplementary tools that were/have been/had been developed to support and manage the library development. The main part of the library is/were/have been/had been written in C++.
What would be the best tense to use in each case?