Amazon MWS Inventory Add Quantity (increment/decrement instead of setting Quantity)

Question

Is there a way (feed) to increase/decrease the inventory quantity instead of setting quantity to an absolute value ?

So instead of

<Quantity>100</Quantity>         => set to inventory qty to 100

use e.g. something like this (incr/decr)

<AddQuantity>10</AddQuantity>    => add 10 to inventory qty

or

<Quantity>+10</Quantity>         => add 10 to inventory qty

Is there any feed or other possibility to do this in MWS ?

Thanks a lot for your answers.

Answer 1

There is no such API - you will have to calculate the new quantity yourself.

You could, however, get an inventory report through MWS first to determine the current quantity in stock (call RequestReport to get a _GET_FLAT_FILE_OPEN_LISTINGS_DATA_)

Sidenote: I find it a bit awkward that Amazon seems to know more about your quantities in stock than your own software...