This is a property of type Text.
{ "type": "PROPERTY_CONSTRAINT_SCHEMA", "constraints": { "type_constraint": "_txt", "allowed_values": [ "Common", "Dwarvish", "Elvish", "Giant", "Gnomish", "Goblin", "Halfling", "Orc", "Draconic", "Common Sign Language", "Abyssal", "Celestial", "Infernal", "Deep Speech", "Primordial", "Sylvan", "Undercommon" ] } }