Knowledge and documents
An agent with no knowledge answers from the model alone, which is how you get confident wrong answers. Documents are what it searches before replying.

Adding a source
Crawling a site
Point the agent at a site and it follows the pages it finds.
PDFs
Keeping it current
Sources can re-sync on a schedule, so a page you edit on your site reaches the agent without anyone re-uploading it.
What the agent does with a document
Documents are turned into questions and answers the agent can search. See FAQ and responses.