API & MCP

Everything a person can do on Scale, Chord and Fretboard Finder, a program or AI agent can do with the same inputs and get the identical result.

HTTP API

POST https://tonegridscalechordfinder.usefulweb.app/api/v1/calculate – run Scale, Chord and Fretboard Finder
GET https://tonegridscalechordfinder.usefulweb.app/api/v1/tool – inputs, output schema, examples
OpenAPI 3.1: /openapi.json · /openapi.yaml
Errors: application/problem+json; 422 includes per-field errors.

Scale, Chord and Fretboard Finder

Spells a scale, mode or chord on any root with correct note names and intervals, marks every position on a guitar, 7-string, bass or ukulele neck in the tuning you choose, lists easy chord shapes and the diatonic chords of a key, or names the chord formed by a set of notes (including inversions). The same theory engine as the Fretboard tab of the Tonegrid app.

Inputs of Scale, Chord and Fretboard Finder
Field	Type	Default	Description
`mode`	select (scale, chord, identify)	"scale"	What do you want?
`root`	select (C, C♯, D, E♭, E, F, F♯, G, A♭, A, B♭, B)	"C"	Root note
`scale`	select (major, minor, dorian, phrygian, lydian, mixolydian, locrian, harmonicMinor, melodicMinor, pentatonic, minorPentatonic, blues, wholeTone, chromatic)	"major"	Scale or mode. Used when showing a scale.
`chord`	select (major, minor, dim, aug, sus2, sus4, power, six, minorSix, dom7, maj7, min7, minMaj7, halfDim7, dim7, sevenSus4, add9, dom9, maj9, min9)	"major"	Chord type. Used when showing a chord.
`notes`	text	—	Notes to name (lowest first). Used when naming a chord: note names separated by spaces, the bass note first. Octave numbers are optional.
`tuning`	select (guitar/standard, guitar/dropD, guitar/halfDown, guitar/dadgad, guitar/openG, guitar/openD, guitar7/standard, bass4/standard, bass4/dropD, bass5/standard, ukulele/standard, ukulele/lowG, ukulel	"guitar/standard"	Instrument and tuning
`frets`	integer	12	Frets to show

Example request

A minor pentatonic on guitar

curl -X POST https://tonegridscalechordfinder.usefulweb.app/api/v1/calculate -H 'content-type: application/json' -d '{"mode":"scale","root":"A","scale":"minorPentatonic","tuning":"guitar/standard","frets":12}'

Every result contains

inputs (normalised, defaults applied), summary, result (validated against the published schema), units, assumptions, sources, warnings, computedAt and links.

MCP (Model Context Protocol)

Streamable HTTP endpoint: https://tonegridscalechordfinder.usefulweb.app/mcp – protocol revisions 2026-07-28 (stateless) and 2025-11-25 / 2025-06-18 / 2025-03-26 (initialize handshake).
Tools: tonegrid_scale_chord_finder
Local stdio connector: node src/mcp-stdio.ts --tool=tonegrid-scale-chord-finder

{
  "mcpServers": {
    "tonegrid-scale-chord-finder": { "type": "http", "url": "https://tonegridscalechordfinder.usefulweb.app/mcp" }
  }
}