How to Get Structured Responses back from OpenAI

OpenAI Tip: If you need structured output from the LLM, use structured responses and define the expected format with JSON Schema.

Here’s an example:

from openai import OpenAI
import os

client = OpenAI(api_key=os.getenv("OPENAI_API_KEY"))

# Define the exact shape you want back.
schema = {
    "name": "acl_parse",
    "schema": {
        "type": "object",
        "properties": {
            "entries": {
                "type": "array",
                "items": {
                    "type": "object",
                    "properties": {
                        "action": {"type": "string"},
                        "protocol": {"type": "string"},
                        "src": {"type": "string"},
                        "dst": {"type": "string"},
                        "port": {"type": "string"},
                    },
                    "required": ["action", "protocol", "src", "dst"],
                },
            }
        },
        "required": ["entries"],
    },
}

acl = """\
permit tcp any host 10.0.0.10 eq 443
deny ip any any
"""

resp = client.chat.completions.create(
    model="gpt-4o-mini",
    messages=[
        {"role": "system", "content": "Parse ACL lines into JSON."},
        {"role": "user", "content": acl},
    ],
    response_format={"type": "json_schema", "json_schema": schema},
)

print(resp.choices[0].message.content)
# Output:
# {
#   "entries": [
#     {
#       "action": "permit",
#       "protocol": "tcp",
#       "src": "any",
#       "dst": "host 10.0.0.10",
#       "port": "eq 443"
#     },
#     {
#       "action": "deny",
#       "protocol": "ip",
#       "src": "any",
#       "dst": "any",
#       "port": ""
#     }
#   ]
# }