Numpy's documentation uses several custom extensions to Sphinx. These are shipped in this numpydoc package, in case you want to make use of them in third-party projects.
The numpydoc extension provides support for the Numpy docstring format in Sphinx, and adds the code description directives np:function, np-c:function, etc. that support the Numpy docstring syntax.
See numpydoc docstring guide for how to write docs that use this extension, and the user guide
Numpydoc inserts a hook into Sphinx's autodoc that converts docstrings following the Numpy/Scipy format to a form palatable to Sphinx.