navidrome-mcp

An MCP server for Navidrome that builds playlists which actually match a described mood, grounded in what you own, what you have listened to, and how you yourself have labelled your music.

Why this exists

Navidrome's API alone cannot do this, for three concrete reasons:

1. Its REST filtering is exact-match only. year=1997 works; year=1990-1999 silently returns nothing. There are no ranges and no AND/OR, so a query like "90s rock I haven't played in a year, max 2 per artist" is not expressible.

2. It keeps no listen history. Only a playCount and a last playDate. There is no way to ask "what do I put on at 7am on a Tuesday".

3. Nothing in the library says how a track feels. Measured on a real 9,311-track library: 32 genres with Rock alone covering 47%, BPM present on 24 tracks (0.3%), ReplayGain on 222 (2%), MusicBrainz recording IDs on 222 (2%). That last number also rules out AcousticBrainz as a primary mood source: its audio-derived mood models are keyed by MBID, and resolving the rest via ISRC → MusicBrainz (rate-limited to 1 req/s) would still only reach ~23% of the library.

So this server maintains its own index and joins three sources:

Only the first is required. Listen history, Last.fm tags and your own playlists each improve ranking and time-of-day fit where they exist, and none of them is load-bearing: the same query means the same thing in a library that has none of them.

Listen history has two failure modes worth knowing about

Both were live here until 2026-08-10, and both are silent.

The history can be a prefix, and used to stay one. ListenBrainz publishes a rate-limit budget on every response (X-RateLimit-Remaining, X-RateLimit-Reset-In; observed 30 requests per 5 seconds). Overrunning it does not return 429. The server stalls responses, first to seconds and then to tens of seconds, and eventually closes the connection (UND_ERR_SOCKET). The walk then stopped and kept its prefix, which is a perfectly valid history: nothing distinguishes a quarter of a large account from all of a small one.

What made that permanent rather than merely unlucky is that the walk always restarted from the newest listen, so every later sync re-fetched what it already had and stopped at the same wall. The index sat at 32k of 126k for months, including through an explicit full resync. Requests are now paced against the published budget, a retry waits for the window to turn over instead of spending what is left of it, and an interrupted walk resumes from the OLDEST listen held. A sync that still cannot finish leaves the index usable and says so, and the next start picks the walk up where it stopped.

One play can arrive twice. Scrobbling to both Last.fm and ListenBrainz while also running ListenBrainz's Last.fm importer delivers every play from two submitters. The timestamps differ, because Last.fm stamps a scrobble when it is submitted and a direct submitter stamps it at playback start, so nothing that keys on an exact time notices. Measured here: a median 219 seconds apart, inflating about a quarter of recent listens. dedupeListens collapses a pair only when a different submitter reported it, since two plays close together from the same submitter are what a genuine repeat looks like. The window and the reasoning are checked by npm run check:dedupe.

LISTENBRAINZ_HISTORY_DAYS bounds a cold start and defaults to effectively the whole account. Note that an incremental sync resumes from the newest listen already held, so listens backfilled with older timestamps need refresh_index with full_listens.

Related MCP server: Navidrome-MCP

Where mood comes from

Not from here. This server has no LLM client and no way to label a track. Mood is produced by navidrome-mood, a Navidrome plugin that judges each track and writes the values into the audio files as tags. This server reads those tags and does everything downstream: filtering, cohesion, sequencing, playlist writing.

The split is deliberate and one-directional. The plugin never calls this server and is useful without it: its tags drive Navidrome's own smart playlists, and Music Assistant and every Subsonic client can read them too. This server depends on the plugin only for mood; install it if you want mood-aware playlists, skip it and everything else still works.

Keeping a second labelling path here as a fallback would mean maintaining the same vocabulary in two languages and shipping two answers to one question. There is deliberately no fallback.

What the plugin writes, per track: energy, valence, intensity, acousticness, density, how fast it feels, whether it is sung, two to four vocabulary terms, the times of day it fits, the vibe regions it falls in, and for a track in none of them, the region it came closest to.

That last one is why mood_vibes_near exists. Region membership is strict, and about a third of a library falls outside every region; most of those are ordinary tracks a little past an edge rather than unusual music between the regions. Setting mood_vibes_near unions them in, which on a 9,195 track library takes the share reachable by region from 65% to 94%. Leave it off when the region's character is the point.

The vocabulary is defined, not derived. Each of its 52 terms carries an explicit anchor in mood-space, and each of the 14 vibes is a named region with a centre and a radius, so the same track gets the same coordinates in anyone's library. Deriving the words from one collection instead would bake that collection's shape into them: a rock-heavy library yields riffy and bass-heavy, which say nothing useful about a jazz one.

The radii are the one part fitted to a collection rather than defined, and the split is deliberate. A centre says what a vibe means and must not move; a radius says how close counts as close, which depends on how tightly the music clusters. Fitting them against an even spread of the coordinate space produced regions wider than the typical gap between any two tracks in a real library, so they are fitted against a measured distribution instead. Coordinates therefore travel between libraries unchanged; region membership is calibrated.

Words alone cannot carry cohesion, which is why the axes exist. Measured on a real library, tender covered both Debussy's Suite bergamasque and Metallica's Nothing Else Matters: both labels correct, and useless as a playlist filter. Distance in mood-space separates them.

Call mood_coverage to see how much of a library is labelled. When the answer is none it says which of the three causes applies (plugin never run, plugin ran but wrote nothing, or tags written but not declared in Navidrome's own config file) because those need different fixes and all three otherwise read as an empty library.

Backfilling Navidrome's play counts

Navidrome counts only what Navidrome served. Its scrobbler is outbound only and IncPlayCount is play_count + 1, so there is no import path: a library listened to for years before Navidrome existed shows a handful of plays, and every smart playlist, client sort and play_count_min filter reads that number rather than the real one. On the library this was built against it was 976 plays against a ListenBrainz history of 123,157 listens.

Run it, and that column becomes the count for everything. Ranking, sorting and the count filters read Navidrome and nothing else; the connector's own listen total stops being scored beside it, because after a backfill the two describe the same plays and weighing both counts the same evidence twice. Skip it and describe_library says so, rather than leaving every ordering quietly wrong.

scripts/ closes the gap. Two steps, because they run in different places:

tsx scripts/plan-playcounts.ts /data/navidrome-mcp/index.json playcounts.json
python3 scripts/apply-playcounts.py playcounts.json /data/navidrome.db          # dry run
python3 scripts/apply-playcounts.py playcounts.json /data/navidrome.db --write

The planner matches the history to tracks with the same key this server uses for everything else, so a fix to the matcher fixes both at once. The applier is standard-library Python because it has to run wherever navidrome.db is, which is often a machine with no node; pointing it at a Docker volume works:

docker run --rm -v <volume>:/data -v "$PWD":/host python:3.12-slim \
  python /host/apply-playcounts.py /host/playcounts.json /data/navidrome.db --write

Five things worth knowing before running it:

• Do not use Navidrome's /rest/scrobble endpoint instead, however much more supported it looks. Navidrome forwards a scrobble to ListenBrainz and Last.fm, so replaying a decade of history through it submits that history back to the service it came from and corrupts it permanently.

• The write is a floor, not an assignment. max(existing, imported) means Navidrome's own counting is never rolled back and a second run changes nothing. Only play_count and play_date are touched; starred and rating share the row and are the user's own judgements.

• A play can land on more than one file. Nothing in a scrobble says which copy was played, so a library holding both a single and an album version credits both. 486 of 7,580 matched tracks were in that position here. Each track's own count stays defensible; the library-wide total is inflated.

• Not every listen matches. 50,781 of 123,157 matched nothing, which is mostly music heard elsewhere and never acquired. The planner reports that number every run: a sudden jump means the matcher broke, not that taste changed.

• Matching on identifiers instead is not the safer option it looks like, and is worth understanding before anyone tries to "fix" the fuzzy match. Two reasons. Coverage: 222 of 9,200 files here carry a genuine MusicBrainz recording id. A further 839 carry a Discogs id in the MusicBrainz-named musicbrainz_trackid tag, which grades as total disagreement against ListenBrainz and means nothing. Semantics: even where both sides hold real ids, they disagree about a third of the time, and the sampled disagreements are all the same song under a different recording, never a different song. ListenBrainz maps a scrobble to its own canonical recording, which is rarely the exact pressing on disk. An id join would therefore reject plays this one correctly credits. It would be more precise and match less.

Design notes

• In-memory index, no database. A full library pull is ~20s for ~10k tracks; once local, every compound query is a single array pass. A JSON snapshot on disk makes restarts instant. Deliberately no native dependency, so it installs under npm ci --ignore-scripts on Node 20.

• The index is a cache, never a source of truth. If the snapshot is missing or unreadable the server just re-syncs.

• It re-syncs itself once it goes stale, half an hour by default, in the background on whatever tool call notices. NAVIDROME_SYNC_TTL_MIN changes the window and 0 turns it off. This is not a nicety: a snapshot that loads cleanly used to be treated as current forever, so music added after the last manual refresh_index never appeared, and a restart did not help. It also catches the gap where the mood plugin labels a track minutes after Navidrome imports it, which otherwise froze that track in the index unlabelled.

• Navidrome's own compound engine is still exposed via create_smart_playlist, for standing playlists that should keep re-evaluating server-side. Note those rules can only see Navidrome's own fields, not ListenBrainz listens or Last.fm tags.

• npm run check:vocab asserts what typechecking cannot about this side's copy of the vocabulary: every synonym resolves and is reachable, no term or region name contains a character Navidrome splits tag values on, and every hour of the day is claimed by some region. The anchors and region geometry live in the plugin and are asserted there.

Tools

Prompt: daylist - refreshes the daylist playlist for the current hour.

Rolling playlists

A rolling playlist is one that gets rewritten on a schedule: daylist hourly, mix: chill and the rest whenever they are asked for. Its title is fixed for its whole life and the phrase that changes goes in the description, which is what commit_playlist enforces: it matches on the title, never renames what it finds, and creates a playlist only when no playlist carries that title yet. A generator that renamed its own output instead would lose track of it and make a new one on the next run, and nobody notices that until the sidebar holds forty near-identical lists.

search_tracks's exclude_recent_runs keeps a rolling playlist off its own recent tracks. It is scoped to one playlist, so the hourly daylist moving fast does not starve the others.

Configuration

Licence

MIT