Reference Documentation Fundamentals
What
Short descriptions of any options/parameters/inputs that can be used with the tool or change how the tool functions. Depending on the tool, these might be able to be automatically generated. For example, many API docs are automatically generated by docstrings within the code.
Why
For intermediate/advanced users, being able to quickly see the details of the option(s) they are looking for is more convenient than having to find them in other locations in the external documentation.
When
Early Development
This documentation should be developed iteratively throughout the project, but starting it early will save time later. For example, if you plan to generate reference documentation from docstrings, establishing a consistent docstring format from the beginning is essential.
Where
In a dedicated section in the external documentation. Depending on the complexity of your tool the reference docs may be a single page or be multiple pages organized into different subsections.
Importance
High