[jameshart]

It is explicit about the fact that that number of decimal places is part of the data.

The semantics for your string “10.00” are complex - is it considered equal to “10”? To “10.000”? To “10.001”?

A user interacting with an API that uses such a string might make all sorts of assumptions about what it supports.

A user interacting with an API that has an explicit decimal places concept is being told ‘decimals matter! They can vary! Here be dragons!’

[lxgr]

> The semantics for your string “10.00” are complex - is it considered equal to “10”?

Yes, but "10 USD" would be a non-canonical representation and you probably serialized incorrectly.

> To “10.000”?

Yes, but same caveat as above applies.

> To “10.001”?

Obviously not, and any system you'd ever want to use in a financial context will tell you so.