The INS - Instituto Nacional de Seguros de Costa Rica (National Insurance Institution) REQUIRES certain Insurance of all drivers in Costa Rica. I’ve had to buy the required protection when I’ve driven across the border into Costa Rica - even with an international Insurance policy.
But the car rental agencies can mark that up by adding on stuff, and of course they will stack on their own various a la carte products marked up ‘til Tuesday. And they’re wiley as hell. ariel_sjo is spot on.
Beware of fuel tanks not full, missing spare tires or tools like jacks or bad bulbs, mirrors, etc. they’ll charge you for. Take photographs - with your phone or camera’s date and time displays on - from every angle, and assure small dings, scratches, windshield pocks and defects are well documented; “We normally won’t charge you for those” becomes “of course you are charged for those - they’re your fault!” Take your time - and be prepared to spend more time than in the US, Europe or Australasia. Be sure everything’s correct and taken care of, from paperwork to car condition. Be nice, or what I call “politely firm”, about this.
And it isn’t unknown for scammers to hang around at the rental lot exit and slash a tire. A few blocks later, you pull over to change the tire, and look, there are friendly Ticos who want to help - themselves, as it turns it they’re using the friendly Tico stereotype to approach you ad rob you.
Nope, this is not typical of Ticos, as we call our Costarricense brothers and sisters - this is the wild and woolly rental car industry’s approach to “wealthy” tourists in too many countries. (I’ve been traveling to C. R. since 1974, have driven my own and rental vehicles, guided nature tours there and will be visiting again next month before the dry season goes away.)