Giving Claude M365 Access via Power Automate and a FastMCP Server
A developer on r/ClaudeAI shared a practical architecture for giving Claude access to Microsoft 365 without tenant admin privileges. The setup uses Power Automate flows as the execution layer, triggered via webhooks, with a small FastMCP server acting as the bridge.
What It Does
Claude can now perform these M365 actions through MCP tools:
- Read inbox and send emails
- Check calendar
- Save notes to OneDrive under specific folders
- Create Planner tasks
- Append rows to Excel spreadsheets
- Fill Word templates
Architecture
The chain is straightforward:
Claude -> MCP tool call -> FastMCP server -> Power Automate webhook -> M365 connectorEach M365 operation is a separate Power Automate flow with an HTTP trigger. The flows run under the user's account, using already-approved permissions. The FastMCP server (about 200 lines of Python + a JSON config file) routes tool calls to the correct webhook URL.
Setup Overview
- Create Power Automate flows for each action (send email, read calendar, etc.) with an HTTP trigger
- Copy the signed webhook URL from each flow
- Deploy a FastMCP server (fastmcp on PyPI) on a cheap VPS
- Define tools like
m365_send_email,m365_calendar_read,onedrive_create_filethat POST JSON to the webhooks - Point Claude Desktop's MCP config at the server
Practical Lessons
The developer notes that agent tool access doesn't require perfect official API integrations — existing enterprise tools like Power Automate can serve as a pragmatic backend. A funny bug: two MCP tools pointing at the same webhook (due to a forgotten URL update in the config) caused Claude to call the 'right' tool but Power Automate performed the wrong action.
📖 Read the full source: r/ClaudeAI
👀 See Also
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