A prototype, for programmers, not for artists or users.
From the README file:
A Gimp plugin that lets plugin programmers view documentation for PDB procedures, GIMP-Python modules, plugins and modules written in Python, and image data. The documentation is live, generated from the code itself and from the current state of GIMP and the PDB.
Copy plugin-inspect.py and the inspector directory to your own, local plugin directory. Make plugin-inspect.py executable. See a comment in plugin-inspect.py for Linux commands.