Python has a PEP (257) that defines Docstring Conventions. Regarding documentation of attributes, it states:

String literals occurring immediately after a simple assignment at the top level of a module, class, or __init__ method are called "attribute docstrings".

So the following are considered documented attributes:

class Foo(object):
  velocity = 1  
  """Foo's initial velocity - class variable"""

  def __init__(self, args):
    self.location = 0.0 
    """Foo's initial location - instance variable"""   

(Edit: Fixed second docstring)

Sphinx ignores docstrings on property setters so all documentation for a property must be on the @property method.

Whilst Sphinx understands certain specific tags (e.g. :param ...:) it will accept any custom tags and will render them as labels for the text which follows them.

Therefore something like the following will render the documentation in a reasonable way (getter, setter and type can be changed to any other text if required).

@property
def name(self):
    """
    The unique name of the direction.

    :getter: Returns this direction's name
    :setter: Sets this direction's name
    :type: string
    """
    return self._name

The generated documentation looks something like this:

class Direction(name) A direction in which movement can be made.

name The unique name of the direction.

Getter: Returns this direction's name

Setter: Sets this direction's name

Type: string

Thanks to @BrenBarm and @A-B-B for pointing me in the direction of this solution.

The property() function returns a special descriptor object:

>>> property()
<property object at 0x10ff07940>

It is this object that has extra methods:

>>> property().getter
<built-in method getter of property object at 0x10ff07998>
>>> property().setter
<built-in method setter of property object at 0x10ff07940>
>>> property().deleter
<built-in method deleter of property object at 0x10ff07998>

These act as decorators too. They return a new property object:

>>> property().getter(None)
<property object at 0x10ff079f0>

that is a copy of the old object, but with one of the functions replaced.

Remember, that the @decorator syntax is just syntactic sugar; the syntax:

@property
def foo(self): return self._foo

really means the same thing as

def foo(self): return self._foo
foo = property(foo)

so foo the function is replaced by property(foo), which we saw above is a special object. Then when you use @foo.setter(), what you are doing is call that property().setter method I showed you above, which returns a new copy of the property, but this time with the setter function replaced with the decorated method.

The following sequence also creates a full-on property, by using those decorator methods.

First we create some functions:

>>> def getter(self): print('Get!')
... 
>>> def setter(self, value): print('Set to {!r}!'.format(value))
... 
>>> def deleter(self): print('Delete!')
... 

Then, we create a property object with only a getter:

>>> prop = property(getter)
>>> prop.fget is getter
True
>>> prop.fset is None
True
>>> prop.fdel is None
True

Next we use the .setter() method to add a setter:

>>> prop = prop.setter(setter)
>>> prop.fget is getter
True
>>> prop.fset is setter
True
>>> prop.fdel is None
True

Last we add a deleter with the .deleter() method:

>>> prop = prop.deleter(deleter)
>>> prop.fget is getter
True
>>> prop.fset is setter
True
>>> prop.fdel is deleter
True

Last but not least, the property object acts as a descriptor object, so it has .__get__(), .__set__() and .__delete__() methods to hook into instance attribute getting, setting and deleting:

>>> class Foo: pass
... 
>>> prop.__get__(Foo(), Foo)
Get!
>>> prop.__set__(Foo(), 'bar')
Set to 'bar'!
>>> prop.__delete__(Foo())
Delete!

The Descriptor Howto includes a pure Python sample implementation of the property() type:

class Property:
    "Emulate PyProperty_Type() in Objects/descrobject.c"

    def __init__(self, fget=None, fset=None, fdel=None, doc=None):
        self.fget = fget
        self.fset = fset
        self.fdel = fdel
        if doc is None and fget is not None:
            doc = fget.__doc__
        self.__doc__ = doc

    def __get__(self, obj, objtype=None):
        if obj is None:
            return self
        if self.fget is None:
            raise AttributeError("unreadable attribute")
        return self.fget(obj)

    def __set__(self, obj, value):
        if self.fset is None:
            raise AttributeError("can't set attribute")
        self.fset(obj, value)

    def __delete__(self, obj):
        if self.fdel is None:
            raise AttributeError("can't delete attribute")
        self.fdel(obj)

    def getter(self, fget):
        return type(self)(fget, self.fset, self.fdel, self.__doc__)

    def setter(self, fset):
        return type(self)(self.fget, fset, self.fdel, self.__doc__)

    def deleter(self, fdel):
        return type(self)(self.fget, self.fset, fdel, self.__doc__)

Write the docstring on the getter, because 1) that's what help(MyClass) shows, and 2) it's also how it's done in the Python docs -- see the x.setter example.

Regarding 1):

class C(object):
    @property
    def x(self):
        """Get x"""
        return getattr(self, '_x', 42)

    @x.setter
    def x(self, value):
        """Set x"""
        self._x = value

And then:

>>> c = C()
>>> help(c)
Help on C in module __main__ object:

class C(__builtin__.object)
 |  Data descriptors defined here:
 |
 |  __dict__
 |      dictionary for instance variables (if defined)
 |
 |  __weakref__
 |      list of weak references to the object (if defined)
 |
 |  x
 |      Get x

>>>

Note that the setter's docstring "Set x" is ignored.

So you should write the docstring for the entire property (getter and setter) on the getter function for it to be visible. An example of a good property docstring might be:

class Serial(object):
    @property
    def baudrate(self):
        """Get or set the current baudrate. Setting the baudrate to a new value
        will reconfigure the serial port automatically.
        """
        return self._baudrate

    @baudrate.setter
    def baudrate(self, value):
        if self._baudrate != value:
            self._baudrate = value
            self._reconfigure_port()