A tool for cleaning a casing tubular (13⅜″) via a narrower casing tubular (9⅝″) or width restriction, has an elongate tool body 1 with axial throughbore 2, box 3 for a corresponding pin 4 to form a tool joint with a workstring 5. In FIG. 1, the body has a nose 6 with fluid discharge channel 7 to pass circulation fluid. An internal shoulder provides a valve seat 8 for a ball 9 passed through the workstring under gravity or during pumping of fluid. Transverse channels 10 receive fluid diverted when the ball is seated within the tool. A side surface 21 has fluid outlet ports 11, and at least one further working surface 22 has tool elements, e.g. bristle-type cleaning elements 23, or scrapers or wipers. Thus the tool body is asymmetrical offering jetting functionality on one side of the tool and mechanical cleaning on the other side.