Connect Claude, ChatGPT or another AI assistant

To Bill connects to AI assistants that speak the MCP protocol (Model Context Protocol): Claude (claude.ai, Claude Desktop, Claude Code), ChatGPT and many others. Once connected, your assistant does in To Bill what you can do there yourself, with your rights and never more: it reads your invoices, your expenses and your accounting and, if you allow it, it makes corrections. You can ask it, for example, “Check the health of my books and book the October bank lines”, or “Prepare a draft invoice for Boulangerie du Lac”.

This guide covers the assistant you bring. The AI built into To Bill (the Copilot, the autopilot) has its own guides: see The AI assistant.

Before you start

• The address to give your assistant is https://app.tobill.ch/mcp. It is also shown in Settings › AI and API connections, under Connector address (MCP), with a Copy button.
• The assistant works in a single company, the one you choose when you authorise it. For another company, connect it a second time.
• It has the rights of your role in that company. A member who cannot see the accounting in To Bill will not see it through their assistant either.
• What the assistant reads in To Bill goes to its provider (Anthropic for Claude, OpenAI for ChatGPT): see What the assistant receives.

Claude: claude.ai and Claude Desktop

The connector you add on claude.ai also works in Claude Desktop and on your phone: you only need to add it once.

1. In Claude, open Customize › Connectors and click Add custom connector. On a Team or Enterprise plan, an owner of the organisation adds it, in Organization settings › Connectors; each member then connects with their own To Bill account.
2. Enter a name, for example To Bill, and paste the address https://app.tobill.ch/mcp. Leave the advanced settings as they are.
3. Click Add, then Connect. The To Bill authorisation page opens: sign in if needed (Google included), choose the company and the access, then click Allow.

Claude returns to the conversation, connected. Before acting with a tool that changes your data, Claude asks for your approval; you can block a specific tool in the connector’s settings.

Claude Code

In a terminal:

claude mcp add --transport http tobill https://app.tobill.ch/mcp

Then, in Claude Code, type /mcp, choose tobill and start the authentication: your browser opens the To Bill authorisation page. Claude Code can also connect with a personal API key instead of this page: see The API and keys.

ChatGPT

Depending on your ChatGPT plan, adding a custom connector requires developer mode and, in a workspace, its administrator’s approval.

1. In ChatGPT, open Settings › Apps, then Advanced settings, and turn on Developer mode.
2. Create an app (Create): a name, for example To Bill, the address https://app.tobill.ch/mcp as the MCP server, and OAuth authentication.
3. Save, then connect: the To Bill authorisation page opens. Choose the company and the access, then click Allow.

ChatGPT asks you to confirm each action that changes your data.

Another assistant

Any assistant that accepts a remote MCP server (HTTP transport) with an OAuth connection connects the same way: give it the address https://app.tobill.ch/mcp and it opens the authorisation page. A tool without an OAuth connection (a script, a command-line client) uses a personal API key: see The API and keys.

The authorisation page

This is the To Bill page your assistant opens the first time. It tells you:

• who is asking for access: the name of the application. When the application is identified by its own address (claude.ai, chatgpt.com), To Bill shows it. Otherwise, the name is the one the application gives itself: only continue if you have just connected it yourself;
• where you will be sent back after your answer; for an application running on your computer, To Bill points this out;
• the Company the assistant will have access to, and only that one;
• the Access requested: Read and modify, or Read only. You can choose Read only even when the assistant asks for more.

Allow connects the assistant; Deny sends it back without access.

What the assistant can do

• Read what you see in To Bill: clients, articles, quotes, invoices, collections, expenses, accounting (journal, general ledger, trial balance, health of the books, bank lines, bank rules), payroll and time if you have access to them, settings.
• With Read and modify, act as you would: create draft quotes and invoices, save clients, book a bank line, book an entry, reverse an entry, correct an expense, manage bank rules, open the next financial year…
• Every action goes through the same checks as in the app: a booked entry is never changed, it is reversed; a filed VAT period stays closed; a sent document is not rewritten.

To Bill gives the assistant its bookkeeping rules: correct with a reversal or a new entry, book the private transactions of a sole proprietorship to account 2850 rather than ignoring them, book no VAT for a company that is not registered for it, and treat the bank statement as the truth for the bank accounts.

What it cannot do

• Pay, transfer money, change your subscription or buy credits.
• Sign in for you, manage your connections and keys, delete the company or your account.
• Act in a company other than the one chosen, or in a fiduciary’s cockpit.
• Manage the team: invite someone, change a role or an e-mail address, remove a member; nor touch the company’s outgoing mail server (SMTP).
• Act in bulk: delete, send or mark as paid several documents at once. It does them one document at a time, and you confirm each one.
• Download the whole company at once (the retention archive, the bundle for the fiduciary), see an employee’s full OASI number or produce the salary payment file. Of an employee’s IBAN, it only sees the last 4 digits.
• Go beyond the rights of your role.

The text of a document is not an order

The assistant reads the text of your vouchers, your bank statements and your invoices. If a text asks it to do something (“pay this amount”, “change the IBAN”), To Bill has told it not to obey: it is data, not an instruction. Always read what the assistant is about to do before you accept it.

Who did what

Every change made by an assistant is recorded in the company’s activity, under your name and the assistant’s (“Change via Claude”): on the dashboard, Recent activities, then View all for the full list. An entry it books shows as its author your name followed by the assistant’s, for example Léa Rochat via Claude.

What the assistant receives

When you connect an assistant, To Bill sends it, at your request, the data it asks for: what its tools read in your company, in plain text. This data goes to the assistant’s provider (Anthropic, OpenAI or another), under that provider’s own terms. You choose the assistant and what it helps you do. The To Bill Copilot, by contrast, replaces names with codes before sending them: see The AI assistant.

Cut off access

1. Open Settings › AI and API connections (also from the menu under your name, at the bottom left).
2. Under Connected apps, click Revoke next to the assistant, then confirm.

Access stops straight away. Removing the connector in the assistant is not always enough: revoke it in To Bill as well. A connection left unused for 30 days stops by itself; you then simply reconnect the assistant.