I used to esearch tool for searching packages in my portage tree, but this tool was not updated for a long time and eventually esearch functionality got broken and tool was maked in the portage tree. Related comment in /usr/portage/profiles/package.mask file says:

# Paul Varner <fuzzyray@gentoo.org> (31 Dec 2008)
# Masked due to being broken with portage 2.1 and 2.2.
# Users can use either the unstable versions or switch to app-portage/eix

I have installed eix, it works well and has more functionality than esearch.

qsearch from app-portage/portage-utils can be used for fast search in portage tree, or standard emerge -s|-S