The field value_type within the field schema would benefit greatly with additional information. This is an important field to determine what kind of log mapping is needed. Documentation here is especially critical because the possible values are not intuitively named. The prime example of this is if you want a "structured" log mapping for a particular field, you must set value_type to equal 'sumofield'.

Additionally, it could be made more clear that setting this field to null is how to configure a "standard" log mapping for a field.