Why AI Agents Cost More Than LLMs (And How to Stop Bleeding Tokens)

I was building a small bookmark app last weekend. You send it a URL, Gemini summarizes and tags the page, the result goes into Postgres. A few hundred lines of TypeScript. The first version cost almost nothing. One LLM call per URL, that's it. Then I added "tools" so the model could fetch pages, look up similar bookmarks, or check things against Google Search. My token bill quadrupled. That's where most people building agents land for the first time. Going from a plain chat call to an agent loop