JSON output

Ask for JSON when your code, not a person, reads the reply. Set response_format to {"type": "json_object"} and describe the fields you want in the prompt.

python

import json
from openai import OpenAI

client = OpenAI(base_url="https://api.continuumlabs.ai/v1", api_key="cl-your-key")

reply = client.chat.completions.create(
    model="glm-5.2",
    temperature=0,
    response_format={"type": "json_object"},
    messages=[
        {"role": "system", "content": 'Extract the invoice. Reply with JSON only: {"supplier": str, "abn": str or null, "total_inc_gst": str}'},
        {"role": "user", "content": "Ironbark Plumbing Pty Ltd, ABN 90 551 661 605. Total (inc GST) $2,856.70"},
    ],
)
invoice = json.loads(reply.choices[0].message.content)

Always check the result in code

JSON mode makes the reply parse as JSON. It does not make it correct. Check it before you use it:

Required fields are present and have the right type.
Allowed values only, for anything that should come from a fixed list.
Copied figures really appear in the source. Models occasionally invent or alter numbers.
Arithmetic is redone in code. For Australian data, the cookbook's checks library tests ABNs, GST and more.

If a check fails, send the problems back and ask for corrected JSON. One retry fixes most errors. If it still fails, flag the item for a person rather than guessing.

The bookkeeper recipe shows the whole pattern on supplier invoices.

Tips

Use temperature: 0 for extraction.
Show the exact field names and types in the system prompt.
Ask the model to copy numbers exactly as written, so your code can check them against the source.