# tag_track Get a compact, HONESTLY-LABELLED tag list for a track — energy / danceability / valence / acousticness / instrumentalness, plus a mood tag and a broad genre tag. It is a tag-shaped projection of the same open-data analysis get_audio_features returns (no audio upload, no extra compute), so it costs the same 1 quota unit, charged only on a served result. The differentiator vs opaque taggers (e.g. Cyanite) is that EVERY tag carries its own confidence and provenance: - confidence: measured (our Essentia analysis) | derived (MIREX mood from valence+energy) | model-estimated (AcousticBrainz mood SVM probability — research-grade, raw prob in value) | catalog-genre (broad catalogue tag, not fine-grained). - provenance: essentia | valence+energy | acousticbrainz | catalog. value is the [0,1] score for numeric tags and null for label-only tags (mood category, genre). Provide AT LEAST ONE identifier: track (optionally with artist), isrc, mbid, spotify_id, or track_id (catalog itunes_track_id). If you know several, send them all — they resolve by precedence (track > isrc > track_id > mbid > spotify_id) and the rest are ignored, so you never have to pick. The broad, reliable coverage is the MEASURED tags from our Essentia analysis over the analysed catalogue (plus on-demand by name); MBID/ISRC additionally reach 7.5M+ AcousticBrainz recordings WHEN you supply that identifier. Returns { track, count, tags:[{tag, category, value, confidence, provenance}], disclaimer }. For the full numeric feature set use get_audio_features; for nearest tracks use a discovery tool. Agent View of the PolicyLayer registry record for `tag_track`. HTML page: https://policylayer.com/tools/com-freqblog-music-metadata/tag-track ## Facts - Tool: `tag_track` - Server: FreqBlog Music Metadata (`https://mcp.freqblog.com/mcp`) — https://policylayer.com/tools/com-freqblog-music-metadata.md - Homepage: https://github.com/https://mcp.freqblog.com/mcp - Risk category: Write (Medium risk) - Registry record: grade D, identity unverified - Server auth posture: open - Server rate-limited: no - Parameters: 6 - Recommended policy verdict: Rate-limited ## Parameters | Parameter | Type | Required | Description | | --- | --- | --- | --- | | `isrc` | object | no | ISRC, e.g. 'USUM71900001'. | | `mbid` | object | no | MusicBrainz recording ID (UUID). Tags come from AcousticBrainz for that exact recording. | | `track` | object | no | Track title. Use with `artist` when known. Supply AT LEAST ONE of track/isrc/mbid/spotify_id/track_id. Sending several is fine — they resolve by precedence (tra | | `artist` | object | no | Artist name. Only used with `track`; improves accuracy. | | `track_id` | object | no | Catalog itunes_track_id from a search_catalog or get_audio_features result. | | `spotify_id` | object | no | Spotify track ID, 'spotify:track:...' URI, or open.spotify.com URL. Resolves ONLY tracks already mapped to a Spotify ID (<1% of the catalog) — prefer track (+ar | Parameters from the server's own tool schema. ## Example call (MCP tools/call, JSON-RPC 2.0) ```json { "jsonrpc": "2.0", "id": 1, "method": "tools/call", "params": { "name": "tag_track", "arguments": {} } } ``` ## Why tag_track is rated Medium An AI agent can call tag_track faster than any human can review: one bad instruction and it creates or modifies resources in FreqBlog Music Metadata by the hundred, each call as confident as the last. ## Use case AI agents use tag_track to create or update resources in FreqBlog Music Metadata, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your FreqBlog Music Metadata environment. ## Recommended policy (PolicyLayer) Verdict: **Rate-limited**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches FreqBlog Music Metadata: ```json { "version": "1", "default": "deny", "tools": { "tag_track": { "limits": [ { "counter": "tag_track_rate", "window": "minute", "max": 30, "scope": "grant" } ] } } } ``` ## Other tools on FreqBlog Music Metadata (11) - `build_setlist` — Read — https://policylayer.com/tools/com-freqblog-music-metadata/build-setlist.md - `find_compatible_keys` — Read — https://policylayer.com/tools/com-freqblog-music-metadata/find-compatible-keys.md - `find_tracks_by_bpm` — Read — https://policylayer.com/tools/com-freqblog-music-metadata/find-tracks-by-bpm.md - `find_tracks_by_key` — Read — https://policylayer.com/tools/com-freqblog-music-metadata/find-tracks-by-key.md - `get_audio_features` — Read — https://policylayer.com/tools/com-freqblog-music-metadata/get-audio-features.md - `get_audio_features_batch` — Read — https://policylayer.com/tools/com-freqblog-music-metadata/get-audio-features-batch.md - `get_recommendations` — Read — https://policylayer.com/tools/com-freqblog-music-metadata/get-recommendations.md - `get_related_artists` — Read — https://policylayer.com/tools/com-freqblog-music-metadata/get-related-artists.md - `score_transition` — Read — https://policylayer.com/tools/com-freqblog-music-metadata/score-transition.md - `search_catalog` — Read — https://policylayer.com/tools/com-freqblog-music-metadata/search-catalog.md - `suggest_next_track` — Read — https://policylayer.com/tools/com-freqblog-music-metadata/suggest-next-track.md ## For agents This record is a snapshot. Live verdicts and the full registry: - Check every server in your MCP config at once: `npx -y policylayer stack` - Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md) - Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events` --- Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=com-freqblog-music-metadata · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/com-freqblog-music-metadata