If you need to ask for a source in the first place, chances are very high that the LLM's response is not based on summarizing existing sources but rather exclusively quoting from memory. That usually goes poorly, in my experience.

The loop "create a research plan, load a few promising search results into context, summarize them with the original question in mind" is vastly superior to "freely associate tokens based on the user's question, and only think about sources once they dig deeper".