{ "openapi": "3.1.1", "info": { "title": "Scale, Chord and Fretboard Finder API", "version": "1.0.0", "summary": "Notes, intervals and fretboard positions of any scale or chord — or name the chord you play.", "description": "Every endpoint performs the same calculation as the human page and returns inputs, result, units, assumptions, sources, warnings and computedAt. MCP endpoint: /mcp." }, "servers": [ { "url": "https://tonegridscalechordfinder.usefulweb.app" } ], "paths": { "/api/v1/calculate": { "post": { "operationId": "calculate", "summary": "Notes, intervals and fretboard positions of any scale or chord — or name the chord you play.", "description": "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.\n\nMethodology:\n- Scales and chords are interval formulas (1, b3, 5, b7 …). The pitch of each note is the root plus the interval in equal-tempered semitones; its name uses the letter that matches the interval’s degree, so a third is always spelled with the third letter above the root (F major contains B♭, D♭ major contains G♭, a diminished seventh may need a double flat).\n- Fretboard positions: every fret of every string whose pitch class belongs to the formula, from standard open-string pitches of the chosen tuning. The ukulele’s standard tuning is re-entrant (the G string is the high G4).\n- Chord shapes: a four-fret window is slid up the neck to fret 15; each string is not played, open or fretted with a chord tone. A shape is kept when the sounding strings are adjacent, the lowest note is the root, every chord tone sounds (a perfect fifth may be left out of four- and five-note chords) and at most four fingers are needed, one of which may barre the lowest fret. Shapes are ranked by fret span, position, muted strings and finger count.\n- Naming a chord: every note is tried as the root against 20 chord formulas; exact pitch-class matches come first, inversions are written as slash chords (C/E) with the first note as the bass, and four-note chords may be recognised without their fifth.\n\nChord shapes are generated by rules, not taken from a chord book: they are playable for most hands but not always the fingering a teacher would choose. Enharmonic spelling follows the chosen root (pick E♭ rather than D♯ for flat keys).", "tags": [ "apps" ], "x-mcp-tool": "tonegrid_scale_chord_finder", "x-owner-app": "tonegrid", "requestBody": { "required": true, "content": { "application/json": { "schema": { "$ref": "#/components/schemas/TonegridScaleChordFinderInput" }, "examples": { "example1": { "summary": "A minor pentatonic on guitar", "value": { "mode": "scale", "root": "A", "scale": "minorPentatonic", "tuning": "guitar/standard", "frets": 12 } }, "example2": { "summary": "E♭ major seventh chord shapes", "value": { "mode": "chord", "root": "E♭", "chord": "maj7", "tuning": "guitar/standard", "frets": 12 } }, "example3": { "summary": "Name the chord E G C (first inversion)", "value": { "mode": "identify", "notes": "E G C", "tuning": "ukulele/standard", "frets": 12 } } } } } }, "responses": { "200": { "description": "Calculation result envelope.", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/TonegridScaleChordFinderResult" } } } }, "400": { "description": "Malformed JSON body.", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } }, "422": { "description": "Invalid input (see errors[]).", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } }, "429": { "description": "Rate limit exceeded (see Retry-After).", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } } } } }, "/api/v1/tool": { "get": { "operationId": "getToolDefinition", "summary": "Inputs, output schema and examples for this tool", "responses": { "200": { "description": "Tool definition.", "content": { "application/json": { "schema": { "type": "object" } } } } } } } }, "components": { "schemas": { "Problem": { "type": "object", "description": "RFC 9457 problem details. 422 responses include per-field `errors`.", "required": [ "type", "title", "status", "detail" ], "properties": { "type": { "type": "string" }, "title": { "type": "string" }, "status": { "type": "integer" }, "detail": { "type": "string" }, "code": { "type": "string" }, "errors": { "type": "array", "items": { "type": "object", "required": [ "field", "message" ], "properties": { "field": { "type": "string" }, "message": { "type": "string" } } } } } }, "TonegridScaleChordFinderInput": { "type": "object", "additionalProperties": false, "properties": { "mode": { "title": "What do you want?", "type": "string", "enum": [ "scale", "chord", "identify" ], "default": "scale" }, "root": { "title": "Root note", "type": "string", "enum": [ "C", "C♯", "D", "E♭", "E", "F", "F♯", "G", "A♭", "A", "B♭", "B" ], "default": "C" }, "scale": { "title": "Scale or mode", "description": "Used when showing a scale.", "type": "string", "enum": [ "major", "minor", "dorian", "phrygian", "lydian", "mixolydian", "locrian", "harmonicMinor", "melodicMinor", "pentatonic", "minorPentatonic", "blues", "wholeTone", "chromatic" ], "default": "major" }, "chord": { "title": "Chord type", "description": "Used when showing a chord.", "type": "string", "enum": [ "major", "minor", "dim", "aug", "sus2", "sus4", "power", "six", "minorSix", "dom7", "maj7", "min7", "minMaj7", "halfDim7", "dim7", "sevenSus4", "add9", "dom9", "maj9", "min9" ], "default": "major" }, "notes": { "title": "Notes to name (lowest first)", "description": "Used when naming a chord: note names separated by spaces, the bass note first. Octave numbers are optional.", "type": "string", "maxLength": 200, "default": "" }, "tuning": { "title": "Instrument and tuning", "type": "string", "enum": [ "guitar/standard", "guitar/dropD", "guitar/halfDown", "guitar/dadgad", "guitar/openG", "guitar/openD", "guitar7/standard", "bass4/standard", "bass4/dropD", "bass5/standard", "ukulele/standard", "ukulele/lowG", "ukulele/baritone" ], "default": "guitar/standard" }, "frets": { "title": "Frets to show", "type": "integer", "minimum": 5, "maximum": 24, "default": 12 } }, "required": [] }, "TonegridScaleChordFinderResult": { "type": "object", "additionalProperties": false, "required": [ "schemaVersion", "tool", "computedAt", "inputs", "summary", "result", "units", "assumptions", "sources", "warnings", "presentation", "links" ], "properties": { "schemaVersion": { "type": "string", "const": "1.0" }, "tool": { "type": "object", "additionalProperties": false, "required": [ "id", "name", "version" ], "properties": { "id": { "type": "string" }, "name": { "type": "string" }, "version": { "type": "string" } } }, "computedAt": { "type": "string", "format": "date-time" }, "inputs": { "type": "object", "description": "Normalised inputs actually used, including applied defaults." }, "summary": { "type": "string" }, "result": { "type": "object", "additionalProperties": false, "required": [ "mode", "title", "instrument", "tuning", "openStrings", "notes", "positions", "diatonic", "voicings", "input", "matches" ], "properties": { "mode": { "type": "string", "enum": [ "scale", "chord", "identify" ] }, "title": { "type": "string" }, "instrument": { "type": "string" }, "tuning": { "type": "string" }, "openStrings": { "type": "array", "items": { "type": "string" }, "description": "Open-string pitches, lowest string (as listed in the tuning) first." }, "notes": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "name", "interval", "intervalName", "semitones" ], "properties": { "name": { "type": "string" }, "interval": { "type": "string", "description": "Interval formula token, e.g. b3 = minor third, #4 = augmented fourth." }, "intervalName": { "type": "string" }, "semitones": { "type": "integer" } } } }, "positions": { "type": "integer", "description": "Positions on the shown part of the neck that belong to the scale or chord." }, "diatonic": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "degree", "roman", "name", "triad", "seventh", "notes" ], "properties": { "degree": { "type": "integer" }, "roman": { "type": "string" }, "name": { "type": "string" }, "triad": { "type": "string" }, "seventh": { "type": "string" }, "notes": { "type": "array", "items": { "type": "string" } } } } }, "voicings": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "shape", "frets", "notes", "lowestFret", "span" ], "properties": { "shape": { "type": "string", "description": "Frets per string, lowest string first; x = not played." }, "frets": { "type": "array", "items": { "type": "integer" } }, "notes": { "type": "array", "items": { "type": "string" } }, "lowestFret": { "type": "integer" }, "span": { "type": "integer" } } } }, "input": { "type": "array", "items": { "type": "string" } }, "matches": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "name", "root", "chord", "inversion", "omitsFifth" ], "properties": { "name": { "type": "string" }, "root": { "type": "string" }, "chord": { "type": "string" }, "inversion": { "type": "boolean" }, "omitsFifth": { "type": "boolean" } } } } } }, "units": { "type": "object", "additionalProperties": { "type": "string" } }, "assumptions": { "type": "array", "items": { "type": "string" } }, "sources": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "title" ], "properties": { "title": { "type": "string" }, "url": { "type": "string" }, "publisher": { "type": "string" }, "retrievedAt": { "type": "string" }, "note": { "type": "string" } } } }, "warnings": { "type": "array", "items": { "type": "string" } }, "presentation": { "type": "array", "items": { "type": "object" }, "description": "Display blocks used by the human page (same data)." }, "links": { "type": "object", "additionalProperties": false, "required": [ "human", "api", "openapi", "methodology" ], "properties": { "human": { "type": "string", "format": "uri" }, "api": { "type": "string", "format": "uri" }, "openapi": { "type": "string", "format": "uri" }, "methodology": { "type": "string", "format": "uri" } } } } } } } }