How to check a KiCAD footprint against KLC (KiCAD library conventions)

First, clone kicad-library-utils using

git clone https://gitlab.com/kicad/libraries/kicad-library-utils.git

Then, run the check script against your footprint – Connector_RJ.pretty/RJ9_Evercom_5301-4P4C.kicad_mod
in this example – using

~/kicad-library-utils/klc-check/check_footprint.py -vv Connector_RJ.pretty/RJ9_Evercom_5301-4P4C.kicad_mod

You might need to adjust the path to kicad-library-utils accordingly.

This will provide colored output on the command line such as

Checking footprint 'RJ9_Evercom_5301-4P4C':
  Violating F5.2 - https://klc.kicad.org/footprint/f5/f5.2/
    Fabrication layer requirements
    Value Label Errors
  Violating F7.2 - https://klc.kicad.org/footprint/f7/f7.2/
    For through-hole components, footprint anchor is set on pad 1
    Pad '1' not located at origin
  Violating F9.1 - https://klc.kicad.org/footprint/f9/f9.1/
    Footprint meta-data is filled in as appropriate
    Value label '5301-4P4C' does not match filename 'RJ9_Evercom_5301-4P4C'
  Violating F9.3 - https://klc.kicad.org/footprint/f9/f9.3/
    Footprint 3D model requirements
    3D model file path missing from the 3D model settings of the footprint