Shard key fields must be ascending, with at most one hashed field. Descending fields are not allowed (SERVER-8129)

When you attempt to create one with a descending field, the error message is confusing

[direct: mongos] test> sh.shardCollection("test.foo", {a:-1})
MongoServerError: Shard key { a: -1 } can contain at most one 'hashed' field, and/or multiple numerical fields set to a value of 1. Failed to parse field a

Can we reword this to be something like

Shard key XXXX can contain at most one 'hashed' field, and/or multiple fields with a value of 1 (ascending). Failed to parse field a

Or modify the code to have different error blocks for "more than one hashed field" and "invalid field value" to make the error message more tailored.