# Music Theory Chord Namer

> Music Theory Chord Namer is a paid API for AI agents from music-theory.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).

Identifies the best chord name, inversion, and alternative names from a set of input notes, treating the first note as the bass.

## Facts

- Endpoint: GET https://music-theory.x402tookit.com/chord-name?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/music-theory-chord-namer-99196cdf
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_r3ducoiTSxvqqzMoiPpIT

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability music-theory-chord-namer-99196cdf
```

Example prompt: What chord is spelled by the notes C E G Bb — give me the best chord name, what inversion it's in, and any alternative names for it.

## When to prefer this

Use this endpoint when you have a set of note names and need to identify the chord they form, including its inversion and alternative names. Prefer it over chord-spelling endpoints (which go symbol→notes) when your input is notes and your output goal is a chord symbol or name.

## Known failure modes

- Invalid or unrecognized note names return an error or null result
- Ambiguous note sets with multiple equally valid interpretations may return degraded=true with caveats
- Fewer than two notes provided may not yield a meaningful chord name
- Non-standard enharmonic spellings may not be recognized
- Network or payment authorization failure returns HTTP 402 or 5xx

## How this service works

Name a chord from its notes (C E G Bb, A C E G): best name, inversion and alternative names; first note is the bass.

## Output

Returns the best chord name (e.g. 'C7'), the inversion number (0 = root position), root note, chord quality, a human-readable summary, alternative chord names, pitch class integers, a boolean for root position, and optional reasons or disclaimers about the identification.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "notes"
     ],
     "properties": {
      "notes": {
       "type": "string",
       "description": "Notes separated by spaces or commas, lowest first: E G C or A C E G"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "bass": {
       "type": [
        "null",
        "string"
       ]
      },
      "best": {
       "type": [
        "null",
        "string"
       ]
      },
      "root": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "quality": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "inversion": {
       "type": [
        "null",
        "number"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "alternatives": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "pitchClasses": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "number"
       }
      },
      "rootPosition": {
       "type": [
        "boolean",
        "null"
       ]
      }
     }
    }
   }

… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/music-theory-chord-namer-99196cdf/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from music-theory.x402tookit.com](https://www.zero.xyz/host/music-theory.x402tookit.com/llms.txt)