This summary is not the rule. The rule text controls.
When someone gets sued and files their own claim back against the person who sued them (called a reconventional demand, similar to a countersuit), they don't need to have the other side formally summoned to court again. The original person who filed the lawsuit is already part of the case, so a new citation isn't required.
Instead, the person filing this counterclaim just needs to deliver a copy of it to the other side using the normal method for sending legal papers, as described in Article 1314. This usually means mailing it or having it delivered to the other person's lawyer if they have one. It can be included as part of the answer to the original lawsuit, or filed as its own separate document.
The main point of this rule is to save time and avoid extra paperwork. Since the plaintiff already knows they're involved in the case, there's no need to start the formal notification process over again. They just need to be properly given a copy of the new claim being made against them.