Claude API from A to Z · Lesson 2
The Messages API structure
system/user/assistant roles, content blocks (text, image), and how a multi-turn conversation works.
Practical exercise
What to do after this lesson
Build a 3-turn conversation by hand (user/assistant/user), send it, and confirm the model remembers context from the first turn. Then add a system instruction and compare the tone of the reply.
Task grader
Build a 3-turn conversation by hand (user/assistant/user), send it, and confirm the model remembers context from the first turn. Then add a system instruction and compare the tone of the reply.
Ready-to-use prompt
Template for this lesson
Copy and adapt to your context. Text in angle brackets should be replaced.
Help me design the messages structure for my scenario. Scenario: <chatbot / agent / classifier> Need conversation memory: <yes/no> Output format: <text / JSON> Show the correct system + messages[] structure and how to add turns.