# Spotify MCP Server — Design Spec

**Date:** 2026-05-22

## Overview

A Python MCP server that exposes Spotify library and playlist management as tools for Claude. Connects via stdio transport (Claude launches it as a subprocess). Authentication uses the OAuth PKCE flow via `spotipy`; tokens are cached locally and auto-refreshed.

## Project Structure

```
mcp-spotify/
├── server.py          # MCP server entry point, tool registrations
├── spotify_client.py  # Thin wrapper around spotipy (auth + API calls)
├── pyproject.toml     # Dependencies: mcp, spotipy, python-dotenv
├── .env.example       # SPOTIPY_CLIENT_ID, SPOTIPY_CLIENT_SECRET, SPOTIPY_REDIRECT_URI
└── README.md          # Setup instructions (creating a Spotify Developer app, registering with Claude Code)
```

## Dependencies

- `mcp` — official MCP Python SDK (stdio server)
- `spotipy` — Spotify Web API client with built-in OAuth and token caching
- `python-dotenv` — load `.env` at startup

## MCP Tools

| Tool | Description | Parameters |
|---|---|---|
| `list_playlists` | List the authenticated user's playlists | — |
| `get_playlist_tracks` | Get all tracks in a playlist with full metadata | `playlist_id: str` |
| `list_saved_tracks` | Get the user's liked/saved tracks | `limit: int = 50` |
| `search_tracks` | Search Spotify for tracks | `query: str`, `limit: int = 10` |
| `create_playlist` | Create a new playlist | `name: str`, `description: str = ""`, `public: bool = False` |
| `add_tracks_to_playlist` | Add tracks to a playlist by URI | `playlist_id: str`, `track_uris: list[str]` |

### Track data returned by `get_playlist_tracks`

Each track entry includes:
- `name` — track title
- `artists` — list of artist names
- `album` — album name
- `duration_ms` — duration in milliseconds
- `duration` — duration formatted as `mm:ss`
- `popularity` — Spotify popularity score (0–100)
- `uri` — Spotify track URI (used to add tracks to playlists)
- `added_at` — ISO timestamp of when the track was added to the playlist

All fields come from a single paginated API call (`playlist_items`); no additional requests needed.

## Authentication

### Setup (once per user)

1. Create a Spotify Developer app at [developer.spotify.com](https://developer.spotify.com)
2. Set the redirect URI to `http://localhost:8888/callback`
3. Copy `.env.example` to `.env` and fill in:
   ```
   SPOTIPY_CLIENT_ID=<your_client_id>
   SPOTIPY_CLIENT_SECRET=<your_client_secret>
   SPOTIPY_REDIRECT_URI=http://localhost:8888/callback
   ```

### First run

`spotify_client.py` initializes `spotipy.Spotify` with `SpotifyOAuth`. spotipy opens the browser to Spotify's auth page. After login, Spotify redirects to `localhost:8888/callback`. spotipy exchanges the code for tokens and caches them to `~/.cache/spotipy/<username>.cache`.

### Subsequent runs

spotipy reads the cached token. If expired, it silently refreshes using the stored refresh token. No browser interaction needed.

### OAuth scopes

```
playlist-read-private
playlist-read-collaborative
playlist-modify-public
playlist-modify-private
user-library-read
```

## Architecture & Data Flow

```
Claude (MCP client)
    │  stdio (JSON-RPC)
    ▼
server.py  (mcp SDK — tool definitions + request routing)
    │  Python function calls
    ▼
spotify_client.py  (spotipy wrapper)
    │  HTTPS
    ▼
Spotify Web API
```

`server.py` owns all MCP concerns: tool schemas, request parsing, response formatting.  
`spotify_client.py` owns all Spotify concerns: auth, API calls, pagination, data shaping.

## Error Handling

- **Startup:** If required env vars are missing, raise immediately with a descriptive message before the server accepts any connections.
- **API errors:** `spotipy` raises `SpotifyException` for all API-level errors. These are caught in `server.py` and returned as MCP error responses containing the HTTP status code and Spotify error message.
- **Token expiry:** Handled transparently by spotipy's `SpotifyOAuth` — no special handling needed.

## Claude Code Registration

Add to `~/.claude/settings.json` (or project `.claude/settings.json`):

```json
{
  "mcpServers": {
    "spotify": {
      "command": "python",
      "args": ["/path/to/mcp-spotify/server.py"],
      "env": {
        "SPOTIPY_CLIENT_ID": "<your_client_id>",
        "SPOTIPY_CLIENT_SECRET": "<your_client_secret>",
        "SPOTIPY_REDIRECT_URI": "http://localhost:8888/callback"
      }
    }
  }
}
```

Alternatively, env vars can be loaded from `.env` by `python-dotenv` and the `env` block omitted.

## Testing

No automated tests. The server is a thin adapter over `spotipy` and the Spotify Web API; mocking the API would test the wrong thing. Verification is done by running the server and calling tools from Claude.