Justdrop MCP

What Justdrop MCP does

Justdrop MCP MCP server gives an AI agent a controlled way to exchange files with devices that have a web browser. The connection is made through JustDrop rooms: the agent creates or joins a room, and a person on another device opens a generated link or scans a QR code. The receiving device does not need an account or a local installation.

The Justdrop MCP MCP server supports both directions. An agent can send files or folders from its allowed local directory, or create a receiving room where files uploaded from another device are saved into a selected directory. Rooms are temporary and designed for one-to-one transfers.

How it works

The drop operation creates a room and registers a public RSA-2048 key before returning the room code, link, and QR code. When the other device joins, it supplies its own key. Each file receives a new AES-256-GCM key, and the file is encrypted for both participants before transfer. Short-lived signed URLs relay encrypted data; the relay does not receive the plaintext or encryption keys.

Delivery is monitored while the room is active. After delivery, the room and its stored data are destroyed, and rooms also have an expiry period. The default expiry is 60 minutes, with a supported range of 1 to 1,440 minutes. Files are encrypted in memory in one pass, so large transfers require enough RAM. Individual files may not exceed 2 GB.

Setup and configuration

The Justdrop MCP MCP server requires Node.js 20 or newer. A stdio MCP client can launch it with npx -y justdrop-mcp; Claude Code can add it with claude mcp add justdrop -- npx -y justdrop-mcp.

Configuration is supplied through environment variables:

• JUSTDROP_ROOT limits every readable or writable path to one directory. If unset, the server uses its working directory.
• JUSTDROP_BASE_URL selects the JustDrop backend and defaults to https://justdrop.ai. Local development can point it to http://localhost:3000.
• JUSTDROP_DEFAULT_EXPIRY_MINUTES sets the default room lifetime and defaults to 60.

Tools and capabilities

• drop sends files or folders and can either create a room or use an existing room_code.
• receive creates or joins a room and saves incoming files in decrypted form.
• status reports peer presence, individual file states, and saved paths as transfer progress changes.
• cancel destroys a room created by the current session, including its files and metadata, or leaves a room that the session joined.

Limitations and notes

The root jail rejects paths that resolve outside JUSTDROP_ROOT. The server also refuses dotfiles, environment files, SSH and TLS keys, keystores, cloud credential files, and shell histories, with no override option. Files with extensions blocked by JustDrop, including executable and batch-file types, are rejected before transfer; zipping them is suggested by the server.

Each drop result provides an explicit list of queued files so the agent can show what will leave the machine. Room codes should be treated as secrets because rooms are one-to-one. The Justdrop MCP MCP server uses ephemeral rooms rather than persistent storage, and its maximum file size is 2 GB.