Build Your First Claude Skill: An Gmail-to-GDrive Receipt Filer in 20 Minutes

Every March, a developer found himself losing a Saturday to digital receipt archaeology, hunting through Gmail for Stripe invoices, AWS bills, and forgotten SaaS subscriptions to reconstruct a year of expenses.

So he built a fix. Using Claude's skill system, he created a simple folder with a single markdown file that instructs Claude to search Gmail for receipts, pull the PDFs, sort them into dated Google Drive folders, and log each one to a CSV file. One command does what used to take hours.

The real insight here is how Claude skills work. They're not complex plugins or coded applications. They're plain text instruction files that Claude loads only when relevant, keeping responses focused and context clean.

The developer learned quickly that precision matters. Vague instructions produce vague results. After a few one-line edits, including a safeguard after Claude once tried to file 800 receipts at 2am, the system has run quietly and reliably ever since.