As with loshon hora, one may not exaggerate rechilus even for a constructive purpose. If a person harmed, or is planning to harm, someone else and the victim must be informed, one may not give him an exaggerated account of what has transpired or is about to occur. This applies even if the person being warned does not take the danger of the situation seriously.
Furthermore, one may relate only as much information as necessary for the purpose to be accomplished. To relate any additional information would be a transgression of the prohibition of rechilus.