Public API

Chord charts from one HTTP request.

Give the API a title, song sections, and chord names. It returns an editable chart link and a direct printable PDF. No account, API key, client registration, or SDK.

Quick start

Create a chart

Send JSON to POST /api/chord-charts. The endpoint is public and accepts cross-origin requests.

curl -X POST https://www.guitarchordbuilder.com/api/chord-charts \
  -H "Content-Type: application/json" \
  -d '{
    "title": "Four-chord song in G",
    "sections": [{
      "name": "Verse",
      "chords": [
        {"name": "G"},
        {"name": "D"},
        {"name": "Em"},
        {"name": "C"}
      ]
    }]
  }'

Response

Return the links

Give the user both URLs. If the LLM client supports file attachments, it can download pdf_url and attach the PDF directly.

{
  "title": "Four-chord song in G",
  "chord_count": 4,
  "share_url": "https://www.guitarchordbuilder.com/?book=...",
  "pdf_url": "https://www.guitarchordbuilder.com/api/chord-charts/pdf?book=...",
  "warnings": []
}

share_url

Editable chart in the browser.

pdf_url

Direct vector PDF for viewing or download.

Input

Chord and fingering support

Up to 12 named sections and 80 chord diagrams per chart.
Major, minor, 7, maj7, m7, sus2, sus4, dim, aug, 6, m6, add9, and slash inversions have standard voicings.
Custom fingerings use six frets ordered from low E to high E, with x for a muted string.
Set accidental spelling to sharp or flat.

Discovery

Machine-readable resources

Point an agent to llms.txt for concise instructions or the OpenAPI 3.1 specification for the complete request schema. The MCP endpoint remains available but is not required.

Can an AI agent generate a chart without MCP?

Yes. An agent with HTTP or shell access can POST a title and chord progression to the public API and return the resulting PDF and share links. No client registration is required. The agent supplies the song progression; the API creates the diagrams and PDF.

Are the chart links stored or private?

The chart data is encoded in each link. No server-side book storage is required, and anyone with the link can open the chart. PDFs are generated on request. Keep the returned URLs intact.