Don't send a CCP 998 settlement offer that requires the opposing party to indemnify you as part of the release (in the event anyone else sues you). Requiring a release is fine, but requiring indemnification makes the 998 offer impossible to value -- because who knows if someone else is going to sue you, or what the defense costs will be of such an action -- and hence makes it unenforceable.
So holds the Court of Appeal today.
Inserting the indemnification provision was a particularly unwise move in the present case, in which the 998 offer was merely for a waiver of costs. No way that offer was going to be accepted anyway, so inserting the indemnity clause didn't really have a point -- it only made the offer not work as a cost-shifting device.
So, in the future, leave that stuff out. Fine for an "informal" settlement offer. Not fine for a 998.