Expose a local MCP server

Before you start

You need an MCP server that speaks HTTP — Streamable HTTP, or the older SSE transport — on a local port, say http://localhost:8000/mcp. A server that only speaks stdio has no port to expose; run it behind an HTTP transport first. And you need the devgate agent with your authtoken added (Quickstart).

Put it online

https:// with no host means your dev domain: every account has one, and its name never changes, so a client you register it with keeps working across restarts. The agent prints the URL; your MCP endpoint is that URL plus the server's path, e.g. https://brave-otter-moon.devgate-free.run/mcp. Without --url you get a random address that changes on every run.

Connect a client

• Claude and ChatGPT — add the URL as a custom connector (the menu names vary between versions). These clients connect from their own servers, which is why the URL has to be public.
• Claude Code — add it as an HTTP server:
  $ claude mcp add --transport http my-tools https://<your-dev-domain>/mcp Copy
• Anything else that speaks Streamable HTTP — Cursor, the MCP Inspector, your own code — takes the same URL.

Every call then shows up in the dashboard's Traffic Inspector; turn on full capture to see the JSON-RPC bodies, which is the quickest way to find out what a client actually sent.

Keep it private

A public URL is reachable by anyone who has it, and an MCP server is often a direct line into your data. If your client can send a header — Claude Code, Cursor and the MCP Inspector can — require a token at the edge, so requests without it never reach your machine. Make one with openssl rand -hex 32, put it in the policy, and keep the file out of git:

on_http_request:
  - expressions:
      - "!('Bearer <your-token>' in getReqHeader('authorization'))"
    actions:
      - type: custom-response
        config:
          status_code: 401
          headers:
            content-type: application/json
            www-authenticate: Bearer
          body: '{"error":"unauthorized"}'

Then give the client the same header:

custom-response costs no Traffic Policy units, so this works on every plan. Hosted connectors can't always send a header of your choosing: for them, put authorization (OAuth) in the MCP server itself, or allow only the provider's published IP ranges with restrict-ips (a paid action, Hobby and up).

If it doesn't connect

• “Tunnel offline” — the agent isn't running, or isn't connected; start it again and keep it running while you use the client.
• 404 — the path is wrong: the server listens on /mcp, /sse or its own path, not the root.
• 403 or “invalid host” — the server checks the Host header to guard against DNS rebinding, and doesn't know your devgate hostname. Add the hostname to its allowed hosts, or start with --host-header=rewrite so it sees localhost:8000 (more on Host headers).
• 401 — the client doesn't send the token, or sends a different one; compare them in the Traffic Inspector.
• 429 — the account went over its per-minute rate limit, usually a client stuck in a retry loop.