Using Claude with your accounting data: connectors explained

What a connector is

A connector links Claude to an outside service. Most connectors use the Model Context Protocol (MCP), an open standard for letting AI assistants call tools and fetch data. A remote connector is a web address, such as https://mcp.nellafinance.co.uk/mcp, that Claude talks to over the internet.

Sign-in uses OAuth. Under the MCP specification, the access token Claude receives is issued for that one connector and must be rejected by any other service. Your accounting software login stays with the connector’s provider and is never passed to Claude.

Adding a connector to Claude

Anthropic’s help centre (checked 31 October 2026) describes the steps:

• Pro and Max: open Customize, then Connectors, choose “+ Add” and then “Add custom connector”.
• Team and Enterprise: an Owner adds it under Organization settings, then Connectors. Members then connect from Customize, then Connectors.
• Free: custom connectors are available, limited to one.

After adding the address you sign in to the provider and approve what the connector may access.

How Claude asks before using tools

Claude asks for your approval before it uses a connector’s tools, and Anthropic advises reviewing those requests carefully. The exception is Research: there, Claude can call connector tools without asking each time. Anthropic suggests turning off write-capable tools when you use Research. For accounting data, that is a sensible default.

Security checklist

• Connect only to providers you trust. A connector can read, and sometimes change, data in the service behind it.
• Review the permissions you are asked to approve at sign-in, and limit them where you can.
• Watch for prompt injection. Text inside invoices or emails could try to steer the assistant; Anthropic flags this risk.
• Turn off tools you do not need in the connector’s settings.
• Know how to disconnect. You can remove a connector from Claude’s Connectors settings at any time.

Questions that work well

• “What is our cash runway at the current burn rate?”
• “Which supplier bills fall due this week, and do any look duplicated?”
• “Walk me through last month’s profit and loss against the month before.”
• “Is the bank reconciled for September?”

Example · illustrative figures

Question: “Which bills are due this week?”
Answer through a connector: “Four bills totalling £7,350 fall due by Friday. Two invoices from the same supplier share an amount (£1,180) and a date, so one may be a duplicate. Cash at bank after these payments would be £40,850.”

Xero’s own Claude integration

Xero announced its own integration with Claude in May 2026. Third-party connectors such as Nella are a separate option and can work across several accounting platforms. The differences are covered in Can ChatGPT or Claude connect to Xero?

Nella’s Claude connector

Nella’s connector answers from Xero, QuickBooks Online, Sage or FreeAgent. Add it in Claude as a custom connector named Nella with the address https://mcp.nellafinance.co.uk/mcp, then sign in with your email or Google. Nella holds the connection to your accounting software; Claude receives only the answer to the question you asked. Nella changes your books only through an entry you approve on Nella’s card; it files nothing, pays nothing and moves no money. The connector is included on every plan, including Nella Free. Full steps are in the Claude help guide.

Using ChatGPT instead? See Using ChatGPT with your accounting data. For how approval works across Nella’s seats, see AI finance agents and human approval.

Sources

• Claude Help Center: Get started with custom connectors using remote MCP
• Model Context Protocol specification: Authorization

Nella provides financial information and education, not accounting or tax advice. Nella shows you the numbers. When a question needs professional judgement, such as a filing or a tax decision, Nella says so and points you to a qualified accountant.