Add a dummy graphic to each mesh line with the appropriate tooltip label and combine them via post-processing:

ParametricPlot[{u Cos[v], u Sin[v]}, {u, 1, 2}, {v, 0, Pi/2},
  Mesh -&gt; {
    Table[{u, Tooltip[Null, u]}, {u, 1, 2, 0.25}],
    Table[{v, Tooltip[Null, v]}, {v, 0, Pi/2, Pi/12}]}
  ] /. {g___, Tooltip[_, label_], l__Line} :&gt; {g, Tooltip[{l}, label]}


Update notice: The pattern was changed from l_Line to l__Line to handle multiple instances of Line in a mesh line, as pointed out by Mr.Wizard in a comment, along with a change in the Tooltip code to handle the sequence l.

Tooltip pointer in ParametricPlots
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One book per answer, please.
