You could override the Description index for your specific type using plone.indexer. This way the catalog has the right information and you don't have to customize the search result.
from plone.indexer import indexer
@indexer(IMyType)
def custom_description(obj, **kw):
return obj.Description[:3]
Register
<adapter name="description" factory=".indexers.custom_description" />
Check plone.indexer documentation on pypi https://pypi.python.org/pypi/plone.indexer