Well, that's the point, isn't it. The RFC basically says "while the JSON grammar allows for arbitrary-precision numbers, don't expect anything larger or more pr

Well, that's the point, isn't it. The RFC basically says "while the JSON grammar allows for arbitrary-precision numbers, don't expect anything larger or more precise than a double, unless you know the recipient uses a more capable implementation". (In other words, JSON numbers are _not_ arbitrary-precision in practice.)