There is a lot of advice to use a landing page to validate your idea before building the product.
This article provides some practical advice on what pages and content you should put on your landing page to validate your idea.
One Page per feature
After creating the home of your landing page for your product, you need to create one page for each feature that you think is worth building.
The home should link to the features, so you can use page views as a proxy of what features are the most wanted.
Link one feature to other features to make navigation and SEO better.
For instance, for OpenPix the features with the most page views as API Pix and Pix WhatsApp.
One Page per article
You need to write as many articles as you can about your new product.
Write articles on how the users will search in Google.
They won't search your product name, nobody knows what your product is.
But they are searching about their problem or similar products.
For instance, for OpenPix, we wrote how to integrate Pix with WhatsApp, not how to integrate OpenPix with WhatsApp.
Link features to articles, and link articles to features.
The article page view also acts as a proxy of what users are looking for, and what you should build first.
All in all
Using a landing page to validate an idea is a good approach.
Despite this, it is not enough.
You also need to build the product you are promising.
Furthermore, you need to talk to each customer individually to understand how they are using the product, and what improvements need to be made.
The structure of this landing page will also help your product to rank well on SEO.
Don't forget to keep updating the landing page, as you progress building the product.