I Gave AI Agents Real Excel. They Did Not Use It Like I Expected - Proven By 90 Days of Telemetry.

90 days of telemetry from an open-source MCP server that drives the actual Excel desktop app. The numbers were not where I thought they would be. Half a year ago I asked a simple question: why can AI agents write a React app from scratch but choke on Revenue Model v27 final final.xlsx ? The answer turned out to be boring and important. Agents had spreadsheet libraries . They did not have Excel . So I built Excel MCP Server : an open-source MCP server that drives the real Excel desktop applicatio