Ah, we still have a way of generating mock APIs: https://retool.com/api-generator. You can upload a CSV (we'll parse the columns and guess types for each one), and then generate mock data and put it into an AIP for you: https://retool.com/utilities/generate-api-from-csv.

In the future, we'd love to make it more robust; we're currently working on a database-y product (think Airtable, but backed by postgres). It would be really cool to have mock data-generation built in to that product.