Provides the statutory basis for the agency, names of officials, and an excellent summary of its activities. Includes laws establishing an agency and laws an agency administers. Difficult to search because of length search results. It is probably better to browse the list of titles. Identify the agency web site.
Most web sites describe missions and programs.
Some also provide agency history. Do not expect an agency web site to discuss its own politics. Use the Subject approach. Historical Tables provides agency appropriations at the cabinet level. Congressional hearings include testimony of agencies on their budget, proposed legislation, and oversight investigations.