Link-only answers are discouraged and often get marked for deletion with a comment of:
While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes.
I've seen some answers in the low-quality review queue, that are short and contain a link, but not in the style of "here's a link to an answer." They're more like stand-alone answers that make sense out of context, and would still be useful without the link. They include recommendations of libraries and tools which can be used to solve the problem given in the question. Such as:
http://stackoverflow.com/a/2768587/298029 (also contains a "You might find this discussion interesting" answer without any link-only comment)
As an example of a stand-alone answer. Here's an answer containing the same sort of text, but no actual link:
Should answers like the above be deleted? If so, does the comment text make sense for them, as it appears to be talking about a different kind of answer? The answers above can be improved more by giving reasons why the linked tools are a good choice instead of including the linked content.