Claude API Tool Use: Function Calling Guide for Production

Thu, 26 Mar 2026 07:00:00 +0100

Tool use is the default pattern for any Claude workload beyond chat. If you are building anything that reads from a database, hits an API, writes a file, or decides between branches of logic, you should be using tools. If you are not, you are probably over-prompting and under-engineering.

I run ten Claude-powered agents in production as bash scripts on a Debian VPS. Every one of them uses tool use, not prompt chaining, to decide what to do next. The model picks a tool, I execute it, I feed the result back, the model continues. That loop is boring, predictable, and debuggable. It beats “parse the JSON out of the model’s free-form answer” every time.

Function-Calling on René Zander | AI Automation Consultant

Claude API Tool Use: Function Calling Guide for Production