list features in docs index

docs/index.rst

@@ -8,9 +8,12 @@ for determining function signatures. This is useful for libraries or tooling
 that want to know how a function can be called: Documentation generators, IDEs,
 and tools that adapt themselves to functions they are given.
 
-``sigtools`` also provides a backport of Python 3's keyword-only parameters and
-function annotations.
+``sigtools`` provides:
 
+- Utilities to boost introspection of callables' signature
+- Backports of Python 3's keyword-only parameters for code that used to maintain both Python 2 and 3 compatibility.
+- Utilities for combining functions, for instance for creating decorators
+- A :doc:`Sphinx <sphinx:usage/index>` extension to make use of improved signature introspection in `sphinx.ext.autodoc`
 
 .. toctree::
     :caption: Guide