The ornamental design for a multi-purpose tool, as shown and described.
FIG. 1 is a perspective view of a multi-purpose tool showing my design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a first side view thereof;
FIG. 5 is a second side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The even-length broken lines are directed to environment, represent unclaimed subject matter, and form no part of the claimed design. The long and short broken lines form an unclaimed boundary around at least a portion of the claimed subject matter and form no part of the claim.