Suggest Substitutions

Tool name: suggest-substitutions

Suggests tritone substitution, secondary dominant, borrowed chords, and modal interchange for a chord in a key.

Annotations

Hint	Value
readOnlyHint	✓
idempotentHint	✓
destructiveHint	—
openWorldHint	—

Input

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "chord": {
      "type": "string",
      "minLength": 1,
      "description": "Chord symbol to suggest substitutions for."
    },
    "key": {
      "type": "string",
      "minLength": 1,
      "description": "Key as \"<tonic> <mode>\" — e.g. \"C major\", \"A minor\"."
    }
  },
  "required": [
    "chord",
    "key"
  ],
  "additionalProperties": false
}

Output

Returned as structuredContent. The text rendering is a short human-readable summary.

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "tritoneSub": {
      "description": "Tritone substitution (only present for dominant-7 chords).",
      "type": "object",
      "properties": {
        "symbol": {
          "type": "string"
        },
        "roman": {
          "type": "string"
        }
      },
      "required": [
        "symbol",
        "roman"
      ],
      "additionalProperties": false
    },
    "secondaryDominant": {
      "description": "Secondary dominant of the input chord (omitted when chord is the key's tonic).",
      "type": "object",
      "properties": {
        "symbol": {
          "type": "string"
        },
        "roman": {
          "type": "string"
        }
      },
      "required": [
        "symbol",
        "roman"
      ],
      "additionalProperties": false
    },
    "borrowedChords": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "symbol": {
            "type": "string"
          },
          "roman": {
            "type": "string"
          },
          "sourceMode": {
            "type": "string",
            "enum": [
              "parallel-minor",
              "parallel-major"
            ]
          }
        },
        "required": [
          "symbol",
          "roman",
          "sourceMode"
        ],
        "additionalProperties": false
      },
      "description": "Chords borrowed from the parallel mode and not already diatonic."
    },
    "modalInterchange": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "symbol": {
            "type": "string"
          },
          "roman": {
            "type": "string"
          },
          "sourceMode": {
            "type": "string",
            "enum": [
              "dorian",
              "mixolydian",
              "phrygian"
            ]
          }
        },
        "required": [
          "symbol",
          "roman",
          "sourceMode"
        ],
        "additionalProperties": false
      },
      "description": "Characteristic chords from parallel Dorian, Mixolydian, and Phrygian modes."
    }
  },
  "required": [
    "borrowedChords",
    "modalInterchange"
  ],
  "additionalProperties": false
}