Use application/vnd.api+json to upload single resource strings or application/vnd.api+json;profile="bulk" to upload resource strings in bulk.

Available only for file-less resources.

Bulk requests need to be applied to the same resource, ie all 'resource' relationships must be identical. Bulk requests do not support partial success, ie either all resource strings will be created, or none will. Consult the error response to figure out which resource strings you need to fix or omit and try again.