Claude for Sheets is an add-on that brings the AI assistant Claude from Anthropic to Google Sheets. It allows users to access Claude's capabilities directly in their spreadsheets. The add-on provides formula functions that can rewrite text, translate, classify, extract information, summarize content, and more. It features automatic caching to reduce API call costs, throttling capability to control API calls, and on-demand and background recalculation for cells. Users need to enter their Anthropic API key to use the add-on, and any API calls made will be billed according to their Anthropic pricing schedule.