Claude in Excel: how it works, MCP connectors, security

Claude in Excel is an Anthropic add-in that puts Claude next to your workbook. You ask questions about cells and formulas, have errors traced and assumptions adjusted, and pull in external data sources through MCP connectors. This article describes how it works, the connectors, the value for your work and the security aspects that are missing from many overviews.

What problem does Claude in Excel solve?

Legacy workbooks with dozens of tabs, hidden assumptions and hardcoded numbers are hard to get your head around. Tracing an error like #REF! or #VALUE! back to its cause quickly costs hours, while the organisation expects answers fast. General AI tools that only see plain text or screenshots miss the structure of formulas and cell references.

What you need is AI that understands the workbook itself, gives targeted explanations or proposes changes, and points to the cells its answer is based on.

What does Claude in Excel do: read, explain, change?

The add-in runs in a side panel next to your workbook. Claude reads the contents of the open file: cells, formulas and tab structure. You ask questions in plain language about specific cells, ranges or the whole model.

Core functionality:

• answering questions about your workbook, with cell references in the answer;
• changing assumptions while formulas and dependencies stay intact;
• debugging errors and pointing to causes;
• setting up new models or templates, or filling existing ones;
• walking through multiple tabs and explaining the links;
• pulling context from external tools, like market data and research, into your spreadsheet through connectors.

Only the workbook you have open in Excel is visible to Claude. Other files are not accessible, unless you upload them or use connectors.

How do MCP connectors work in Excel?

The add-in talks to Excel through its object model: cells, ranges, formulas and tabs are read and, after your approval, can be changed. Supported file formats are .xlsx and .xlsm. Formulas, dependencies and existing formatting are kept where possible.

Claude in Excel can use the same connectors as in your Claude settings. Through the Model Context Protocol (MCP), Claude can fetch context from external sources like S&P Global, LSEG, Daloopa, Pitchbook, Moody's and FactSet. What an MCP link is in practice, you can also read at our integrations page. In broad terms the data flows like this: (1) the workbook contents and any connector context go to the model, (2) the model sends tool calls back to Excel, for example changing a cell or writing a formula. For financial models or due diligence you can weigh both your spreadsheet and market or company data in one conversation.

You set up connectors in the Claude settings; once they are there, they work in Excel too. Custom connectors can bring extra risk. Assess them against the guidelines for remote MCP before you use them.

What does it deliver?

The value is not in automating everything, but in cutting time: understanding faster what a workbook does, tracing errors faster and changing assumptions more safely. That raises trust in your numbers.

• Model review: get to grips with a legacy model faster than by tracing back by hand.
• Debugging: have the cause of #REF!, #VALUE! or circular references explained and targeted fixes proposed, which you still approve.
• Scenarios: "Raise the growth assumption by 2% and show the impact on terminal value", without breaking formulas.
• Documentation: have a short summary made per tab or model for handover or governance.

Claude does not replace domain knowledge: you stay responsible for the outcomes. It is a tool for understanding and maintenance, not for unsupervised automation. Want to go beyond Excel and automate other business processes too? Read about AI implementation with AI agents.

How do you install Claude in Excel?

1. Go to the Claude page in Microsoft AppSource and choose "Get it now" to install the add-in.
2. Open Excel and activate the add-in via Home > Add-ins (Windows) or Tools > Add-ins (Mac).
3. Sign in with your Claude account (Pro, Max, Team or Enterprise; the free version of Claude does not support Claude in Excel).
4. Open an existing workbook and start with questions about structure and formulas before you let it make changes.

You open the panel with Ctrl+Option+C (Mac) or Ctrl+Alt+C (Windows). Organisations can arrange management and rollout through the Microsoft 365 Admin Center, under Settings, Integrated apps, Add-ins; search for "Claude by Anthropic for Excel".

How safe is Claude in Excel, and what is prompt injection?

Claude in Excel only changes something after your explicit approval. Every proposed change is shown and you can accept or refuse it. Still, Anthropic warns about prompt injection through the spreadsheet itself: malicious or unintended instructions in cells, formulas or comments can push the model into unwanted actions, like exporting or changing data. So only use workbooks you trust: your own files, approved templates and internal models.

Some functions carry extra risk and can show a confirmation window, among them WEBSERVICE, STOCKHISTORY, IMPORTDATA, IMPORTXML, INDIRECT, DDE, CALL, EVALUATE, FORMULA, IMAGE, FILES, FOPEN, FWRITE, REGISTER.ID, RTD and INFO. They can fetch external data, access files or run code.

How do you handle context and sessions?

Longer conversations are shortened automatically to stay within the context limits. Older parts of the conversation are then no longer fully available to the model.

• With very large workbooks or long modelling sessions the context can fill up. Then start a new conversation for a new task or a new part of the model.
• The optional Claude Log tab records which actions Claude has run in the sheet. That helps with review and audit, especially in teams.
• Chat history is not kept between sessions: every time you open the add-in, you start a new conversation. So save important explanations or conclusions yourself.

What can Claude in Excel not do?

Claude in Excel does not support data tables, macros or VBA. Power Query and Power Pivot are not explained or changed. For audit-critical calculations or final client deliverables, human review is a must. Anthropic advises against using it for final deliverables without review, or for models with very sensitive data without proper controls.

Frequently asked questions

What exactly is Claude in Excel?

Claude in Excel is a Microsoft add-in from Anthropic. It runs next to your workbook and answers questions about cells, formulas and structure. You do not write code: asking questions in plain language is enough. It is available to Claude Pro, Max, Team and Enterprise subscribers.

Which MCP connectors are available for Excel?

Connectors you have set up in Claude, like S&P Global, LSEG, Pitchbook, Moody's and Egnyte, also work in Excel. You configure them once in your Claude account settings.

Is Claude in Excel safe for sensitive company data?

Claude only changes something after your approval. Watch for prompt injection: do not use the add-in on workbooks from external or unknown sources. For regulated data, follow your organisation's policy.

Does Claude in Excel support macros and VBA?

No. Claude works with cells, formulas and tab structure in .xlsx and .xlsm, but does not read or change VBA code or macros.

Is my chat history kept in Claude in Excel?

No. Every session starts with a new conversation. Record important explanations or conclusions yourself. Team and Enterprise may have different retention settings; ask your admin.

Where do you go from here?

Claude in Excel puts Claude next to your workbook: reading, explaining, adjusting assumptions and tracing errors, with connectors for external context. The value is in faster understanding and less error-prone changes, not in full automation. Want to know where else AI saves time in your company? Make an AI scan with the UnifyAI Agent or plan an introduction.