Design and build the tools

Build 5 tools with clear names, descriptions and typed inputs: get_sales(start, end, product), get_stock(product), list_low_stock(days_ahead), get_expenses(month, category), create_purchase_order(product, qty) (draft only). Prefer specific tools over one 'run any SQL' tool; if you add a SQL tool, make it read-only. Return short, clear results (and errors as text the model can understand).