Upnext

What upnext MCP server does

The upnext MCP server lets an MCP-compatible agent manage a queue whose entries can resolve to different audio sources. A queue may contain a Spotify track, a web audio URL, a local file, or the media currently playing on the machine. Items are handled in order, so an agent can add new audio without replacing the listener’s current playback immediately.

The package is the MCP-facing version of the broader upnext runtime. It exposes twelve tools for queue and playback operations. The README specifically identifies media_adopt_current, which adds the machine’s current media to the queue. That allows an agent to continue from existing playback rather than interrupting it.

How it works

The runtime owns the queue rather than delegating the entire list to Spotify, Apple Music, or a browser element. Adapters resolve individual entries when they reach the front, and the runtime can try another suitable adapter if the first one cannot load an item. This supports mixed queues and fallback between available sources.

Capability checks are part of the model. Operations such as seeking, pausing, changing volume, searching, or starting a specific item depend on the adapter currently handling playback. Unsupported actions are reported as unavailable. Playback completion may be detected by an event or by polling, depending on the source.

The server can reach the sources supported by the installed desktop setup: Spotify desktop on macOS or Spotify Web API, controlled browser media elements, local files and streams, Apple Music through the Music app, and current machine playback on macOS or Linux. The MCP package itself is intended to give agents access to that same setup.

Setup and configuration

Run the server through npx in an MCP client configuration:

{
  "mcpServers": {
    "upnext": {
      "command": "npx",
      "args": ["-y", "upnext-mcp"]
    }
  }
}

The server depends on the adapters and applications available on the host. For local playback, the local adapter uses ffplay from FFmpeg or afplay on macOS. Spotify desktop control requires the macOS app; Spotify Web API access uses a token held by the user.

Tools and capabilities

The upnext MCP server provides twelve tools for interacting with the shared audio runtime. Based on the documented runtime and example behavior, the integration is intended for queueing media, starting or advancing playback, and inspecting or controlling playback where the active adapter supports those operations. The documented media_adopt_current tool imports currently playing media into the queue.

The underlying runtime also supports queue persistence through serialization and restoration, event notifications for item start and completion, capability queries, and fallback when an adapter cannot load an entry.

Limitations and notes

Source support is not uniform. Current machine playback can be adopted and observed but cannot start a requested track. Spotify desktop cannot search its catalog through its AppleScript interface, while Spotify Web API and Apple Music provide search support under their documented conditions. The local adapter’s search requires a configured music folder index.

The now-playing adapter supports macOS and Linux, not Windows. Controlling one particular browser tab is not implemented; browser support is for media elements the application controls. Some sources allow external changes to playback, and position reporting may be estimated or polled rather than exact. The project is licensed under Apache-2.0.