DOC: Provide migration notes for scalar inspection functions

doc/source/numpy_2_0_migration_guide.rst

@@ -92,27 +92,29 @@ geterrobj               Use the np.errstate context manager instead.
 Inf                     Use ``np.inf`` instead.
 Infinity                Use ``np.inf`` instead.
 infty                   Use ``np.inf`` instead.
-issctype
+issctype                Use ``issubclass(rep, np.generic)`` instead.
 issubclass\_            Use ``issubclass`` builtin instead.
 issubsctype             Use ``np.issubdtype`` instead.
 mat                     Use ``np.asmatrix`` instead.
-maximum_sctype
+maximum_sctype          Use a specific dtype instead. You should avoid relying
+                        on any implicit mechanism and select the largest dtype of
+                        a kind explicitly in the code.
 NaN                     Use ``np.nan`` instead.
 nbytes                  Use ``np.dtype(<dtype>).itemsize`` instead.
 NINF                    Use ``-np.inf`` instead.
 NZERO                   Use ``-0.0`` instead.
 longcomplex             Use ``np.clongdouble`` instead.
-longfloat               Use ``np.longdouble`` instead.      
+longfloat               Use ``np.longdouble`` instead.
 lookfor                 Search NumPy's documentation directly.
-obj2sctype
+obj2sctype              Use ``np.dtype(obj).type`` instead.
 PINF                    Use ``np.inf`` instead.
 PZERO                   Use ``0.0`` instead.
 recfromcsv              Use ``np.genfromtxt`` with comma delimiter instead.
 recfromtxt              Use ``np.genfromtxt`` instead.
 round\_                 Use ``np.round`` instead.
 safe_eval               Use ``ast.literal_eval`` instead.
-sctype2char
-sctypes
+sctype2char             Use ``np.dtype(obj).char`` instead.
+sctypes                 Access dtypes explicitly instead.
 seterrobj               Use the np.errstate context manager instead.
 set_numeric_ops         For the general case, use ``PyUFunc_ReplaceLoopBySignature``. 
                         For ndarray subclasses, define the ``__array_ufunc__`` method 

numpy/_expired_attrs_2_0.py

@@ -40,11 +40,14 @@
     "Infinity": "Use `np.inf` instead.",
     "NaN": "Use `np.nan` instead.",
     "infty": "Use `np.inf` instead.",
-    "issctype": "",
-    "maximum_sctype": "",
-    "obj2sctype": "",
-    "sctype2char": "",
-    "sctypes": "",
+    "issctype": "Use `issubclass(rep, np.generic)` instead.",
+    "maximum_sctype":
+        "Use a specific dtype instead. You should avoid relying "
+        "on any implicit mechanism and select the largest dtype of "
+        "a kind explicitly in the code.",
+    "obj2sctype": "Use `np.dtype(obj).type` instead.",
+    "sctype2char": "Use `np.dtype(obj).char` instead.",
+    "sctypes": "Access dtypes explicitly instead.",
     "issubsctype": "Use `np.issubdtype` instead.",
     "set_string_function": 
         "Use `np.set_printoptions` instead with a formatter for "