@responsively/mcp

MCP (Model Context Protocol) server for Responsively App — lets AI coding agents like Claude Code and Cursor drive the app: load URLs, manage device previews, read and interact with pages, and capture per-device screenshots to visually verify responsive layouts.

The app is launched on demand. Connecting an agent session does not open the app; the first tool call starts it automatically (and it stays open afterwards). If it's already running, it's reused.

Setup

Install Responsively App and launch it once. Then:

Claude Code

claude mcp add responsively -- npx -y @responsively/mcp

Cursor (.cursor/mcp.json)

{
  "mcpServers": {
    "responsively": {"command": "npx", "args": ["-y", "@responsively/mcp"]}
  }
}

Tools

| Tool | Description | | --- | --- | | get_app_state | Current URL, page title, layout, zoom and active devices | | navigate | Load a URL in all device previews (waits for the page to load) | | list_devices | Full device catalog, including custom devices | | set_active_devices | Change which devices are previewed, by id or name | | screenshot | Capture one or all device previews as JPEG images | | read_page | Read a preview's page text and interactive elements with CSS selectors | | click | Click an element (trusted mouse event; mirrors across previews) | | type_text | Type into a form field with real keystrokes, optionally press Enter |

How it works

This package is a thin bootstrap: the actual MCP bridge ships inside the installed app (version-locked to it). The bootstrap finds the install — via a location file the app writes on startup — and runs that bridge in-process.

Environment variables

| Variable | Purpose | | --- | --- | | RESPONSIVELY_APP_PATH | Path to a custom app install (auto-detected otherwise) | | RESPONSIVELY_MCP_PORT | Port of the app's MCP server (default 12720) | | RESPONSIVELY_MCP_BRIDGE | Direct path to a bridge cli.js (development override) |

Note for Linux: the app ships as an AppImage, so launch it once before first use — that's how the bootstrap learns where it lives.

License

MIT