# GPT structured output and PDF input: JSON Schema and response_format

Source: https://ofox.ai/docs/develop/models/gpt/structured-output

This page covers structured output and PDF input for the GPT family. For model IDs and endpoint setup, see the [GPT family overview](https://ofox.ai/docs/develop/models/gpt).

## Structured output
Pass a JSON Schema in `response_format`; with `strict: true`, the output strictly conforms to the schema:

```python filename="gpt_json_schema.py"
import json
import os
from openai import OpenAI

client = OpenAI(base_url="https://api.ofox.ai/v1", api_key=os.environ["OFOX_API_KEY"])

resp = client.chat.completions.create(
    model="openai/gpt-5.4-mini",
    response_format={
        "type": "json_schema",
        "json_schema": {
            "name": "price",
            "strict": True,
            "schema": {
                "type": "object",
                "properties": {"price": {"type": "number"}, "currency": {"type": "string"}},
                "required": ["price", "currency"],
                "additionalProperties": False,
            },
        },
    },
    messages=[{"role": "user", "content": "A bat and a ball cost $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?"}],
)
print(json.loads(resp.choices[0].message.content))
```

For more patterns, see [Structured output](https://ofox.ai/docs/develop/guides/structured-output).

## PDF input

**Chat Completions**

```python filename="gpt_pdf.py"
import base64
import os
from openai import OpenAI

client = OpenAI(base_url="https://api.ofox.ai/v1", api_key=os.environ["OFOX_API_KEY"])
pdf_b64 = base64.b64encode(open("invoice.pdf", "rb").read()).decode()

resp = client.chat.completions.create(
    model="openai/gpt-5.4-mini",
    messages=[{"role": "user", "content": [
        {"type": "file", "file": {"filename": "invoice.pdf", "file_data": f"data:application/pdf;base64,{pdf_b64}"}},
        {"type": "text", "text": "What is the total amount on this invoice?"},
    ]}],
)
print(resp.choices[0].message.content)
```

**Responses**

```python filename="gpt_pdf_responses.py"
import base64
import os
from openai import OpenAI

client = OpenAI(base_url="https://api.ofox.ai/v1", api_key=os.environ["OFOX_API_KEY"])
pdf_b64 = base64.b64encode(open("invoice.pdf", "rb").read()).decode()

resp = client.responses.create(
    model="openai/gpt-5.4-mini",
    input=[{"role": "user", "content": [
        {"type": "input_file", "filename": "invoice.pdf", "file_data": f"data:application/pdf;base64,{pdf_b64}"},
        {"type": "input_text", "text": "What is the total amount on this invoice?"},
    ]}],
)
print(resp.output_text)
```

For other errors, see [Common errors](https://ofox.ai/docs/develop/models/gpt#errors).