bfg-llmutil 0.5.0

A set of utility functions to handle LLM structural output

llmutil

This library provides tools to generate structured output and function calls from the OpenAI API.

What is Structured Output?

Structured Output is the recommended method for getting formatted responses. It guarantees that outputs follow your defined schema, making it more reliable than previous methods like JSON mode, function calls, or tool use.

How to Use

Structured Output

To use Structured Output, you need to define a schema. This library makes it easy with simple type definitions:

from llmutil import new_response

output = new_response(
    [
        {
            "role": "user",
            "content": "normalize this address: 1 hacker way, menlo park, california",
        }
    ],
    model="gpt-4.1-mini",
    schema={
        "street": "string",
        "city": "string",
        "state": "string",
    },
)

# {'type': 'message', 'content': {'street': '1 Hacker Way', 'city': 'Menlo Park', 'state': 'CA'}}
print(output["content"])

Function Calls

You can also use function calls to give the model access to tools:

from llmutil import new_response, build_function_call_messages

def add(a, b):
    return a + b

tools = {
    "add": {
        "a": "number",
        "b": "number",
    }
}

messages = [
    {
        "role": "system",
        "content": "you cannot do math. you must use the add() function to add numbers.",
    },
    {
        "role": "user",
        "content": "alice has 10 apples, bob has 20 apples, how many apples do they have in total?",
    },
]

output = new_response(messages, model="gpt-4.1-mini", tools=tools)

# {'type': 'function_call', 'name': 'add', 'args': {'a': 10, 'b': 20}}
print(output)

# Execute the function and continue the conversation
output["result"] = add(output["args"]["a"], output["args"]["b"])
output = new_response(
    messages + build_function_call_messages(output),
    model="gpt-4.1-mini",
    tools=tools,
)

# {'type': 'message', 'content': 'Alice and Bob have 30 apples in total.'}
print(output)