Critical Role Rule on Healing Spellcast-Clarification

Can anyone clarify the rule for a healer using a Healing Domain requiring a Spellcast roll and succeeds with a critical success roll. How does the mechanics of the Crit change the outcome of the healing? I cannot find this in the core rule book but I may not be searching the correct terms. Thank you!

There is no Healing Domain. Splendor is the Domain typically associated with healing, and offers a healing spell card at 1 level. The Domain Card’s describe the nature of their associated features, including any rolls needed and the effects.

Thank you for your reply, perhaps I was unclear in my question. My player used the Domain Effect “Healing Hands” which states: " Make a Spellcast Roll (13) and target a creature other than yourself in melee. On a success, mark a Stress to heal the target 2 Hit Points or 2 Stress . On a failure, mark a Stress to heal the target 1 Hit Point or 1 Stress . You can’t heal the same target again until after your next long rest"

He rolled a Crit on his Spellcast Roll. How do any of you interpret a Crit in a situation like this? I could not find a rule for Critting on a beneficial ability such as healing a player. Thank you.

If it doesn’t state a a crit stipulation in the text, treat a crit as a success with hope. Your GM might allow an extra benefit, but the RAW is simply what’s on the card.