Currently you can only search for two keywords at a time. Shellsink uses Google App Engine (GAE) as the underlying technology. The keyword search implementation provided by GAE is currently quite limited. There is: no substring matching, limited number of keywords and only fields of 500 characters or less are indexable. I know. It is a bummer. Unfortunately, search is a complex problem and I don't have the brains to solve it. I'm going to wait for google to solve it. I predict later versions of the App Engine APIs will improve the search functionality and I look forward to removing these limitations just as soon as Google does.
