What is MCP and how does flexx use it?

MCP (Model Context Protocol) is an open standard that lets AI agents interact with external tools. flexx turns your machine into an MCP server — AI agents like Cursor, Claude, and ChatGPT can read files, run commands, and edit code on your machine through the relay.

Which AI tools work with flexx?

Any tool that supports the Model Context Protocol (MCP) works with flexx. This includes Cursor, Claude Desktop, ChatGPT with MCP plugins, OpenAI Codex, and any custom MCP client.

Can I use flexx without installing anything?

Yes — for Memory. Create a free account and connect any MCP client; the memory tools need no install and no machine. Remote tools (files, shell, screenshots, tunnels) only become available after you install the flexx CLI on a machine and connect it.

Is my machine exposed to the internet?

No. Your machine only makes outbound WebSocket connections to the relay. Zero inbound ports are opened. The relay mediates all communication between AI agents and your machine.

How do I connect Cursor to my machine via MCP?

Install flexx (curl -fsSL https://cli.flexx.dev/install.sh | sh), run 'flexx setup', then add the MCP server URL https://relay.flexx.dev/v1/mcp in Cursor Settings → MCP → Add Server. OAuth authentication is handled automatically.

Yes. The free tier includes unlimited remotes, unlimited MCP tools, SSH access, and localhost tunneling. Managed and team tiers with additional features are coming soon.

MCP Configuration for AI Agents

Configure Cursor, Claude Desktop, ChatGPT, OpenAI Codex, and other MCP-compatible AI tools to connect to your machine via flexx. Includes config snippets and the complete list of available MCP tools.

What is MCP?

Model Context Protocol is an open standard for AI agents to interact with external tools. flexx exposes your machine's capabilities as MCP tools that any compatible agent can call.

Your MCP endpoint

After running flexx setup, your MCP endpoint is:

https://relay.flexx.dev/v1/mcp

Authentication is handled via OAuth 2.1 with PKCE — your AI tool will prompt you to approve access through a consent flow in the dashboard.

Which tools you get depends on what is connected

The memory tools are available as soon as you connect — no machine required. The remote tools (files, shell, screenshots, tunnels) appear once a machine with the flexx CLI is online. See Memory for the full story.

That holds at the consent screen too: with no machine registered you can still approve the request — Remote Access starts switched off, Memory is granted, and the client connects immediately. Run flexx connect on a machine whenever you want the rest, then re-authorize the client to add Remote Access.

Configure your AI tool

Cursor

Open Settings → MCP → Add Server
Set the URL to:

https://relay.flexx.dev/v1/mcp

Cursor handles OAuth authentication automatically. You'll be prompted to approve access on first connection.

Claude Desktop

Add to ~/.claude/mcp_servers.json:

{
  "flexx": {
    "url": "https://relay.flexx.dev/v1/mcp"
  }
}

ChatGPT

Use the MCP endpoint URL directly in your ChatGPT MCP tool configuration:

https://relay.flexx.dev/v1/mcp

OAuth 2.1 with PKCE is supported — ChatGPT will handle the consent flow automatically.

OpenAI Codex

Add flexx as an MCP server in your Codex configuration:

https://relay.flexx.dev/v1/mcp

Any MCP client

flexx works with any tool that supports the Model Context Protocol standard:

Setting	Value
Endpoint URL	`https://relay.flexx.dev/v1/mcp`
Protocol	MCP (Model Context Protocol)
Authentication	OAuth 2.1 with PKCE
Transport	HTTP + Server-Sent Events

Tool	Description
`read_file`	Read file contents (supports offset and limit)
`write_file`	Write or create files
`list_directory`	List files and subdirectories
`delete_file`	Delete a file
`glob_files`	Find files matching glob patterns (e.g., `*/.ts`)

Code editing

Tool	Description
`str_replace`	Find and replace text in files (exact string match)

Shell

Tool	Description
`execute_command`	Run shell commands with configurable timeout. Supports optional `cwd` parameter to run from a subdirectory.

Search

Tool	Description
`grep_files`	Search file contents using ripgrep (requires ripgrep installed)

Screenshots

Tool	Description
`screenshot_url`	Capture a full-page screenshot of a URL (requires Chrome/Chromium)
`screenshot_element`	Capture a specific DOM element by CSS selector

Tunneling

Tool	Description
`tunnel_start`	Expose a local port via a public URL through the relay
`tunnel_stop`	Stop an active tunnel
`tunnel_list`	List all active tunnels

System

Tool	Description
`health_check`	Check daemon health and connectivity

Authentication flow

AI Agent
  │
  ├─ Connects to relay.flexx.dev/v1/mcp
  ├─ OAuth 2.1 + PKCE consent flow
  ├─ User approves access and selects remote
  ▼
Relay (relay.flexx.dev)
  │
  ├─ Validates OAuth token
  ├─ Routes to selected remote
  ▼
Your Machine (flexx daemon)
  │
  ├─ Executes MCP tool
  ├─ Returns result
  ▼
Relay → AI Agent

During the consent flow, you choose which remote machine the AI agent connects to. You can revoke access at any time from Dashboard → Settings.

OAuth scopes

Scope	Permission
`remotes:read`	View your connected machines and their status
`remotes:write`	Register, update, and remove machines
`tools:execute`	Run MCP tools on your machines
`profile:read`	View your account email and organization

Security

All communication is encrypted (WSS/HTTPS)
Your machine only makes outbound connections
OAuth 2.1 with PKCE prevents token interception
Tools respect workspace path scoping
Commands are filtered through a blocklist
File operations have size limits