You're question is phrased oddly.

Unsure if you're trying to...

1) Auto post Facebook content to a WordPress site... or...

2) Auto post WordPress content to a Facebook page.

My guess is #2, so you'll use https://hootsuite.com or something similar.

You must be very careful about how exactly you do this, as you'll either destroy your WordPress site SEO or Facebook page SEO.

Before you start down this path, best hire someone like a Fractional CMO (Chief Marketing Officer) to go through your entire online ecosystem + money flow, to ensure you're optimizing your marketing aligned with your exact income goals.

It depends on what you mean by sharing to Facebook through their API. There are several options to do that.

The first way is if you are using a Wordpress plugin shares through the API, either through a share button on the site or automatically sharing new pages or posts that are published. Some of the plugins I've seen will automatically pull in the title of the page or post from Wordpress as the text. However, Facebook made some changes a while back that made it mandatory to allow a user to input their own text. So the text is editable.

The second way is if you're building an integration yourself. If you know what to do with the code, then it's pretty easy to automatically pull in the page/post name. However, as mentioned above you have to make it so that the person who's sharing has the ability to edit the text. Otherwise your integration is not likely to get approved when you submit it.