Tools

mcpFortyTwo registers every tool through a single fan-out in src/mcp/tools/index.ts. Each tool ships:

A Zod input schema validated at call time.
A Zod output schema mirrored into the response’s structuredContent.
A human-readable text rendering returned as the tool’s content block.

All pages below are generated directly from those definitions, so they cannot drift from the live server.

Music theory

Atomic queries against tonal: chords, scales, keys, modes, intervals.

get-chord Parse a chord symbol → root, quality, notes, intervals, extensions, bass.

get-scale Spell a scale and its mode characteristics.

get-key Diatonic chords, signature and scale notes for a key.

get-mode Detailed information about a single mode.

get-interval Interval between two pitches with both shorthand and English names.

get-note-info Enharmonic, frequency, MIDI number and octave for a note.

get-diatonic-chords The seven diatonic chords for a key, with Roman-numeral functions.

get-progression Expand a Roman-numeral progression in a key.

analyze-progression Roman-numeral / functional analysis of a sequence of chords.

analyze-voice-leading Voice-leading distance, parallels and common-tone retention.

detect-key Best-fit key for a list of chords or notes, with confidence.

transpose Transpose a single chord or note by an interval.

transpose-progression Transpose an entire progression preserving voicings.

suggest-substitutions Reharmonization candidates (tritone, secondary dominant, modal interchange…).

Knowledge graph

Curated catalogue stored in Postgres, queried via Drizzle.

search-progressions Filter the progression catalogue by name, key, function or tag.

search-modes Find modes by family, brightness or characteristic interval.

list-cadences Enumerate canonical cadences with their Roman-numeral patterns.

list-voicings Available voicings for the MIDI generators (closed, drop-2, shell, …).

MIDI generation

Each generator returns a Standard MIDI File Type 1 (480 PPQ) as a base64 string plus metadata. Decode with base64 -d > out.mid and drop into any DAW.

generate-progression-midi Chord progression with selectable voicing, tempo and time signature.

generate-scale-midi A scale run across one or more octaves.

generate-arpeggio-midi Arpeggiated chord pattern (up, down, alternating, etc.).

generate-bassline-midi Bassline that follows a progression — root, walking, or pattern-based.

generate-drum-pattern-midi Drum pattern on GM channel 10 (kick/snare/hat/etc.).