3Accessing Claude with the API
Structured data exercise
2 min read304 words
Time: 10–15 minutes
Get hands-on with the prefill + stop_sequence pattern by extracting a clean, parseable JSON object from Claude and validating it with json.loads().
Step 1—Write the Prompt
Pick a realistic target shape. A good candidate: a user profile with name, role, years_experience, and a skills array of three to five strings.
Create a fresh messages list and append a user message that asks Claude to generate that object. Be explicit about the field names you want — vague prompts produce inconsistent keys.
messages = []
add_user_message(
messages,
"Generate a JSON object for a fictional senior engineer with fields: "
"name, role, years_experience, and skills (an array of 3-5 strings)."
)
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You can now reliably extract clean, machine-readable structured data from Claude for use in any application.