Search Across Indices
ItemSearch requests require that you specify a search index.
This is because searching across the millions of products in Amazon databases would
take too long. Product Advertising API does, however, enable you to search across multiple search
indices using the All or Blended search indices.
All Search Index
You can use the All search index to do an
ItemSearch search through all search indices. There are,
however, a number of restrictions placed on this request: the only parameter
that you can use in the request is
Keywords, and you
cannot, for example, sort results.