Random Generators on World Anvil are complex, but can achieve great results if done right.
In order to fill a generator with data it is necessary to collect and curate this data first. Provide links to lists on a website with public resources or create and share a Google Sheet. This will form the basis for any generator or template.
Create a weighted graph that shows how the collected data influences each other while generating.
In order to create prose descriptions, variant text templates are needed. These text templates then have specific words which can be randomized. The more variation the text templates have the more varied the results will be.