Building on the Claude API
Developers moving from using Claude in chat to building products on it
Prerequisites: Comfortable in one programming language. A Claude API key. Modules 02 and 18 help but are not required.
Last verified 2026-07-10
Executive summary
You will learn the Claude API from first call to first agent: messages, system prompts, streaming, tool use, and structured output. End state is a small working application — an API integration with at least one tool Claude calls — running against your own key. After this module you can choose the right model (Fable, Opus, Sonnet, Haiku) for a task, estimate and control costs, and build the request patterns every production integration rests on. This is the API leg of Anthropic's Claude Certified Developer exam.
Learning objectives
- Make and debug Messages API calls: roles, system prompts, multi-turn conversations
- Stream responses and handle stop reasons correctly
- Define tools and handle the tool-use loop
- Get reliable structured output for downstream code
- Pick models deliberately and reason about token costs
Prefer the live room?
This module also runs inside our in-person bootcamps and workshops in Copenhagen.