Indexing webpages on google

i need to index some webpages on google. i searched a bit and i came with two options:

1 - add a sitemap, but we want to do this dinamically, so, isn't the best approach for us.

2 - use the following api POST https://indexing.googleapis.com/v3/urlNotifications:publish

have someone used this ? i have did a request to index a webpage but without success!

if i use the "URL Inspection" on google search console it works.. but we need to do this over api. Someone have an idea of what i'm doing wrong ?