Current version of the schema is available at https://sb-ncbr.github.io/tunnels-schema/schemas/mmcif_tunnels_v10.dic.
See the full version with the descriptions.
After updating the dictionary, check whether the file is valid:
gemmi validate -v mmcif_tunnels_v10.dic
loop_
_audit_conform.dict_name
_audit_conform.dict_version
_audit_conform.dict_location
mmcif_tunnels.dic 1.0 https://sb-ncbr.github.io/tunnels-schema/schemas/mmcif_tunnels_v10.dic
gemmi validate -v -d mmcif_tunnels_v10.dic structure.cif