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External MCP servers

MCP (Model Context Protocol) is a standard way for an app to offer tools to an AI assistant. Many services now publish an MCP server — accounting, payments, market data, a full web browser — and connecting one gives Lucius whatever tools that server offers.

This is the most powerful connector in the app, and the one that deserves the most care: a server you connect is someone else’s software, and what it returns goes straight into Lucius’s conversation. Only connect servers you trust, and start every tool at Needs approval (the default).

There are two kinds:

  • Remote server (URL) — a service hosted by the vendor. You give its address and, usually, sign in or paste a key.
  • Local command (stdio) — a program the app starts on this machine, such as npx -y @playwright/mcp@latest. It runs with the same access to this computer as Open Net Worth itself.

Add a server from the directory

The directory includes ready-made entries — Playwright (a real web browser), Firecrawl, Stripe, QuickBooks Online, Xero, Mercury, Interactive Brokers, Robinhood, moomoo, Alpaca MCP, Coinbase, OKX, Kraken, Expensify, Avalara AvaTax, Twelve Data, SEC EDGAR and FRED.

Each connector shows coloured tags for what it’s for, such as Brokerage, Banking or Web search. Searching the Connectors page matches those tags too. In Browse & add, click a category in the row of small tags under All · Channels · Data sources · Web · MCP, or click a tag on any card, to see only that kind; click it again (or All) to clear it. On a phone the category tags sit behind the filter icon beside search, which lights up while one is picked. A server you’ve already added shows once, with a settings gear instead of +. Suggested lists up to three connectors you haven’t added yet — Email, Telegram, Plaid, Interactive Brokers and Coinbase first — once at the bottom of All, or under the section on a single tab such as MCP — and on a tab with nothing set up yet, inside its empty view, under Browse & add — and at the top of Browse & add before you search or filter; click one to read about it and add it. Sort orders the full list below it: Popular puts the connectors you’ve added first, then popular ones, then the rest A–Z.

  1. Open Connectors in the sidebar, click Browse & add, and choose MCP.
  2. Click a card to read what it does and which tools it offers, then click Add. The connection form opens with the address or command already filled in.
  3. Fill in what the server needs:
    • OAuth servers (Mercury, Interactive Brokers, Robinhood, moomoo, Expensify, Avalara, Twelve Data): click Connect and sign in to the vendor in the window that opens.
    • API key servers (Stripe): paste the key into API key. For Stripe, a restricted key with only the permissions you want is the safer choice.
    • Local commands with Environment variables (optional) pre-listed (Firecrawl, Xero, SEC EDGAR, FRED, Alpaca MCP, Coinbase, OKX, Kraken): fill in the value after each =, for example FRED_API_KEY=abc123. Get the value from the vendor — the card’s Documentation or Source repository link says where. The trading ones start without real money where the vendor offers that: Alpaca MCP on paper trading, OKX with --demo in its arguments, Kraken with only market data, a read-only account and paper trading; the card says how to switch. A value that is a private key (-----BEGIN … KEY----- … -----END … KEY-----) can be pasted as it is — over several lines, on one line, or with \n in place of the line breaks, the way a downloaded JSON key file holds it; the app rebuilds it into a key the server can read. Coinbase needs Node.js 22 or later and a key created at portal.cdp.coinbase.com with Signature algorithm: ECDSA (Advanced Trade refuses the default Ed25519 key): its key name (organizations/…/apiKeys/…) goes in COINBASE_KEY_ID and its private key in COINBASE_KEY_SECRET. Alpaca MCP needs uv; Kraken needs the Kraken CLI installed first (macOS or Linux).
  4. Click Connect. The app starts the server, checks it answers, and lists its tools — Testing connection to … and listing tools…. A local command can take a few minutes the first time while its package downloads.
  5. Review the tools it found. Each starts at Needs approval; change any to Always allow or Blocked if you want. Click Add server.

The toast ”… added — N tools ready for Lucius” confirms it. Nothing is saved until the connection test succeeds.

QuickBooks Online has no ready-made settings — follow the links on its card for the vendor’s own instructions, and enter what they give you in the form (or add it as a custom server, below).

Add any other server

  1. Connectors → Browse & add → MCP → Custom MCP server.
  2. If the server’s README has a JSON config block (the "mcpServers": { … } kind), click Paste from a config snippet and paste it — the fields below fill themselves in. Otherwise:
  3. Pick a Transport:
    • Remote server (URL) — enter the Server URL (starting with https://, or http:// for a server on your own machine), then choose Authentication: None, API key (sent to the server as a bearer token), or OAuth (you sign in to the vendor in a pop-up). A line under the menu says what each choice is for. If you pick the wrong one, the error says which the server wants — for example “This server needs you to sign in” — with a button that switches it for you. If no sign-in window appears, click Open the sign-in page under “Waiting for sign-in…”; the screen picks up the result once you finish, whichever window you signed in from.
    • Local command (stdio) — enter the Command (for example npx or uvx), the Arguments (for example -y @modelcontextprotocol/server-filesystem /path/to/folder) and any Environment variables, one NAME=value per line (a private key may span several lines).
  4. Click Connect, review the tools, and click Add server — the same as steps 4–5 above.

A local command needs its runtime installed on the machine running Open Net Worth — Node.js for npx, uv for uvx.

For a remote server, Open Net Worth fills in a readable name and icon from what the server says about itself, or else from its website, instead of its bare address. That’s what the site says about itself, not a check of who runs the server, so the badge still reads Unknown publisher. A name you typed yourself is never replaced. ⋯ → Refresh tools list reads the name and icon again.

Check that it works

Ask Lucius to use it, for example after adding Playwright:

Open example.com in the browser and tell me what the page says.

The first time he uses each tool, you’ll get a card to approve it. The server’s page under Connectors lists its tools and their levels under Tool permissions.

Managing a server

Open the server under Connectors:

  • ⋯ (More actions) → Edit configuration — change the address, key, command or environment. The connection is tested again before anything is saved. A saved key is never sent back to your browser, so to re-test with it, reveal it with the eye icon or paste it again. The transport can’t be changed — add the server again instead.
  • ⋯ → Refresh tools list — pick up tools the server added since you connected it.
  • Pause / Resume — Lucius loses access to its tools while paused. Resuming a server that has never listed its tools connects to it and lists them; if it can’t be reached, it shows an error instead of Connected.
  • ⋯ → Remove connector — removes the server and its saved credentials.
  • Reconnect — appears if the server stopped answering or a sign-in expired.

Permissions — start cautious

Every tool from an MCP server starts at Needs approval: Lucius shows you exactly what he’s about to call and waits for you. You can change each tool’s level under Tool permissions, or by choosing Always allow on an approval card. See Permissions.

Tools are listed under Read-only tools or Write & delete tools. When the server marks a tool as read-only (or not), that’s the heading it gets; otherwise the app guesses from the tool’s name. The heading is only a label. It never changes a tool’s level or whether a call runs.

Always allow really means always — including inside a scheduled Automation with nobody watching. Only use it for a tool you’ve used enough to trust, and never for one that can change or send things (a payment, an invoice, an email) unless you’re sure. Remember the vendor can update their server at any time.

Risks, in plain terms

  • A local command can do anything you can do on this machine — read and write your files, use the network. It runs for as long as the connector is enabled, not just during a call. Only add commands from sources you trust, like any software you install.
  • A server’s answers can try to trick Lucius. Text from a third-party server is treated as data, never as instructions from you, and is cleaned and shortened before Lucius sees it. That lowers the risk; it doesn’t remove it — which is why approval is the default.
  • Some servers write to real accounts. Stripe, QuickBooks, Xero and Mercury tools can create or change records in those services, and Interactive Brokers, Robinhood, moomoo, Alpaca MCP, Coinbase, OKX and Kraken tools can place orders (Robinhood only in a separate agent account it opens for you). The directory card says so when that’s the case. For a server you run with an API key, the key’s own permissions are the limit — create it with only what you want allowed.

What protects you:

  • Lucius never sees the server’s full address or command line — only its host or program name — because a connection string often contains a password or key. You see the full details on the Connectors page.
  • Lucius can’t add a server, change one, or raise a tool’s permission. Only you can, from the Connectors page.
  • Keys, OAuth sign-ins and environment variables are stored on this machine only, never sent to the AI model, and left out of exports and sanitised backups.

Troubleshooting

“Could not reach the server.” — check the URL or command is right and the server is running. For a local command, the box under the spinner shows the command’s own output; an error there (for example command not found) usually means Node.js or uv isn’t installed.

“Enter a full URL, starting with http:// or https://.” — include the https:// part.

The test fails with an authorization error — the server needs credentials. Switch Authentication to API key or OAuth and try again.

OAuth: “Register this redirect URI with the vendor, then try again” — the vendor needs you to set up an app on their side. Register the address shown, then click Connect again.

OAuth: a Client ID field appears — this server doesn’t support automatic sign-up. Create an app registration at the vendor, paste its client ID, and try again.

“Sign in above, then test the connection.” — finish the OAuth sign-in before clicking Connect again.

Was connected — sign-in expired — click Reconnect (or Edit configuration) and sign in again.

It hangs on a first connect — a local command may still be downloading. If the output box has been quiet for a long time, click ‹ Back at the top, check the command, and try again.