[corobo]

It's fair but the worry comes in with what happens if I run out of units of work and send a new article. Does it reject the article and I miss out? Does it charge as and when I send an article[1]? Do I get charged extra for unexpected usage?

If I have to ponder any one of these questions I'd just switch to a different app, there's a fair few that provide this functionality

[1] In this case the main worry is what if I accidentally somehow send every tab I have open to this service through a bug or something? Do I pay or does the app maker take one for the team?