MSG rules

21 rules, each with its source

The rules the free checker and the Distributor API run. Each one has a stable ID, a normative statement, the exact test, live examples and the published guidance it comes from. Cite a rule by its ID.

Credits & featured artists

FEAT_FORMAT Featured credit must be lowercase 'feat.' or 'with' in parentheses/brackets track_title Apple Music Style Guide FEAT_IN_ARTIST Primary artist field must not contain feat./with/& joins; one artist per field artist Spotify metadata guidelines FEAT_IN_TITLE Prefer FeaturedArtist role over featuring text in title track_title Spotify metadata guidelines FEAT_MISMATCH Featured artist in title not present in featured_artists field track_title Spotify metadata guidelines

Titles & versions

VERSION_PARENS Version descriptors go in parentheses track_title Apple Music Style Guide ALL_CAPS No ALL CAPS / all lowercase titles track_title Apple Music Style Guide EMOJI No emoji in metadata track_title Apple Music Style Guide EXCESS_PUNCT Repeated/decorative punctuation track_title Apple Music Style Guide DUPLICATE_TITLE Duplicate track titles within release/batch track_title Spotify Newsroom, Sep 2025

Spam & metadata gaming

KEYWORD_STUFFING SEO/keyword-stuffed title track_title Spotify metadata guidelines PROMO_TEXT Promotional / DSP-name text in metadata track_title Apple Music Style Guide GENERIC_ARTIST Generic / SEO-term artist name artist Spotify metadata guidelines SHORT_DURATION Very short track duration Spotify Newsroom, Sep 2025

Identifiers

ISRC_FORMAT ISRC must be CC-XXX-YY-NNNNN isrc ISRC structure (IFPI) ISRC_DUPLICATE Same ISRC on different titles in batch isrc ISRC agency: when not to assign UPC_FORMAT UPC-A check digit fails upc GS1 check digit

Flags, language & genre

EXPLICIT_FLAG Explicit flag must be set explicit Spotify explicit content LANGUAGE Language should be set as ISO 639 code language ISO 639-2 GENRE_MISSING Primary genre missing genre Apple Music Style Guide

AI disclosure

AI_DISCLOSURE_MISSING No AI-use disclosure ai_use DDEX ERN 4.3.2 AI_SIGNAL_UNDISCLOSED AI-tool keywords track_title Spotify AI credits

Severity: errors block delivery, warnings are worth fixing, info is advisory. The identity test and escape patterns in the MSG style guidelines are applied in review and are not automated rules.