When encoding types for requests like this, I'm exactly as strict as I need to be: no more, no less. Any assumption about the shape of the data that my code will make is encoded in the parser, but the parser is very generous with everything else.
For example, if a request has a field I didn't expect, that's not an error, I simply ignore that field because I obviously didn't need it. Likewise if requests start using a more specific schema, such as now sending only positive integers. If, however, the schema changes such that a field I rely on is dropped or changes type, my code will eventually fail anyway as soon as it makes an assumption about the data. Why not fail at the point of entry instead of saving it for later?