MP3Tag export script for generating a JSON, updated for my usage and JSONLint validation

JSON.mte

$filename(json,utf-8){$loop(%_filename_ext%)$puts(CountMax,%_counter%)$loopend()
    "numSongs": $get(CountMax),
    "songs": '['
$loop(%_filename_ext%)        {
            "title": "%title%",
            "album": "%album%",
            "artist": "%artist%",
            "album_artist": "%albumartist%",
            "composer": "$meta(composer,1)",
            "publisher": "%publisher%",
            "year": $left(%year%,4),
            "track": $num(%track%,1),
            "comment": "%comment%",

            "codec": "%_codec%",
            "bitrate": $mul(%_bitrate%,1000),
            "vbr": $if($or($eql(%_vbr%,VBR),$eql(%_tag%,FLAC)),true,false),
            "mode": "%_mode%",
            "samplerate": %_samplerate%,
            "length_seconds": %_length_seconds%,

            "tag": "%_tag%",
            "tag_read": "%_tag_read%",
            "tag_size": %_tag_size%,
            "tag_size_appended": %_tag_size_appended%,
            "tag_size_prepended": %_tag_size_prepended%,
            "id3v2_encoding": "%_id3v2_character_encoding%",

            "filename": "%_filename%",
            "extension": "%_extension%",
            "location": "$regexp(%_folderpath%,'\\','\\\\')",
            "directory": "%_directory%",
            "file_size": %_file_size_bytes%,

            "bpm": %bpm%,
            "bpm_start": %BPM_START%,
            "fBPM": %fbpm%,

            "key_start": "%key_start%",
            "key_end": "%key_end%",
            "initial_key": "%initialkey%",
            "content_group_description": "%contentgroup%",

            "genres": '['$if(%genre%,"$meta_sep(genre,"', '")",)']',

            "composers": '['$if(%composer%,"$meta_sep(composer,"', '")",)']',

            "covers": '['$if($grtr(%_covers%,0),
                {
                    "mimetype": $if2("%_cover_mimetype%",null)','
                    "type": $if2("%_cover_type%",null)','
                    "size": $if2(%_cover_size%,0)
                }
            ,)'],'

            "n_genres": $if(%genre%,$add($len($regexp($meta(genre),'[^,]',)),1),0),
            "n_composers": $if(%composer%,$add($len($regexp($meta(composer),'[^,]',)),1),0),
            "n_covers": $if2(%_covers%,0)
        }$if($eql($get(CountMax),%_counter%),,',')
$loopend()    ']'
}