Otis

Otis is a client-billing MCP server built and run by Boon IT SRL. It keeps work, expenses, invoices and payments as records that an AI assistant reads and writes over MCP, with no separate app or dashboard. The site states that this version is free.

What It Is

Otis is a record-keeping and rules-enforcement layer for freelancers and small businesses who bill clients. Instead of a billing interface, the user connects the server URL to an assistant such as Claude, ChatGPT, Claude Code, Codex or Cursor, signs in with an email code, and asks the assistant to log work, start timers, record expenses, draft and issue invoices, and record payments. Otis runs no AI model of its own; the assistant does the reasoning and writing.

How the billing workflow works

The docs describe 25 typed tools covering clients, billable work, timers, expenses, invoices, payments, business and tax settings, export and feedback. Amounts are stored as integer minor units, a draft reserves work so it is billed only once, and an invoice is issued only when the user confirms its exact total. Otherwise Otis refuses with a TOTAL_CHANGED error. Repeated requests with the same request ID are not counted twice. Exports return records and audit history as paginated JSON, which an assistant can turn into a CSV for an accountant.

Boundaries and data handling

Otis does not send invoices or take payments; the assistant can produce an invoice document, and the user reports payments back. It stores the tax treatment the user confirms and provides dated setup guides for the US, Canada, the UK and Australia, but does not decide what is owed. Business records are stored per business in Cloudflare's EU jurisdiction and encrypted at rest. Sign-in uses OAuth with PKCE and one-time email codes.

Open-source deployment model

The docs state Otis is open source under the MIT License, with the MCP server and website in one repository and a Claude and Codex plugin in another. The About page says users can export records at any time or run the code themselves.