You're likely to need additional information about applications because of the limitations of the resources installed by default. Debian's dpkg and dpkg-query commands give detailed information about the packages and associated files on your system, but are of limited use with other packages.
Read it here
The main disadvantage of the Debian and Ubuntu search pages — aside from the fact that your Internet connection might occasionally be down, or the pages offline for maintenance — is the fact that you have to drill down three or four pages to find the information you want. This limitation is what makes the recently released Ubuntu Simple Package Crawler (USPC) potentially so attractive. Currently at version 0.4, USPC is approximately a KDE equivalent of the search engine found on the Ubuntu Web searcher. It can search on release and architecture, and list dependencies, but dispenses with the “recommends” and “suggests” categories — an omission that makes missing handy additions all too easy. For some reason, it also has an option to omit from search results any package that is installed by default in Ubuntu — perhaps on the grounds that such basic software should not be lightly updated. All the same, if USPC eventually provides more of the options that the Web searchers do, it may become a welcome addition to Ubuntu's search tools, and one that I hope is imported to Debian as well.