justai 5.5.3

Makes working with LLMs like OpenAI GPT, Anthropic Claude, Google Gemini and Open source models super easy

JustAI

Package to make working with Large Language Models in Python super easy. Supports OpenAI, Anthropic Claude, Google Gemini, X Grok, DeepSeek, Perplexity, Reve, OpenRouter and local GGUF models.

Author: Hans-Peter Harmsen ([e-mail])
Current version: 5.5.3

Installation

1. Install the package:

pip install justai

2. Create an API key for the provider(s) you intend to use:

   • OpenAI: platform.openai.com
   • Anthropic: console.anthropic.com
   • Google: aistudio.google.com
   • X AI: console.x.ai
   • DeepSeek: platform.deepseek.com

3. Create a .env file with the relevant keys:

OPENAI_API_KEY=your-openai-api-key
ANTHROPIC_API_KEY=your-anthropic-api-key
GOOGLE_API_KEY=your-google-api-key
X_API_KEY=your-x-ai-api-key
DEEPSEEK_API_KEY=your-deepseek-api-key
PERPLEXITY_API_KEY=your-perplexity-api-key

Basic usage

from justai import Model

model = Model('gpt-5-mini')
model.system = """You are a movie critic. I feed you with movie
                  titles and you give me a review in 50 words."""

response = model.chat("Forrest Gump", cached=True)
print(response)

The cached=True parameter tells justai to cache the prompt and response locally.

Models

The provider is chosen automatically based on the model name prefix:

Prefix	Provider
gpt*, o1*, o3*	OpenAI
claude*	Anthropic
gemini*	Google
grok*	X AI
deepseek*	DeepSeek
sonar*	Perplexity
reve*	Reve
openrouter/*	OpenRouter
*.gguf	Local GGUF

Features

JSON and structured output

model = Model('gemini-2.5-flash')
prompt = 'Give me the main characters from Seinfeld. Return json with keys name, profession and weirdness'
data = model.chat(prompt, return_json=True)

For typed structured output, pass a Pydantic model or Python type as response_format:

from pydantic import BaseModel as PydanticModel

class Character(PydanticModel):
    name: str
    profession: str
    weirdness: str

result = model.chat(prompt, response_format=list[Character])

Images

Pass images as URLs, raw bytes or PIL images:

model = Model('gpt-5-nano')
url = 'https://upload.wikimedia.org/wikipedia/commons/9/94/Common_dolphin.jpg'
message = model.chat("What is in this image", images=url)

Image generation

model = Model('gpt-5')
pil_image = model.generate_image("A dolphin reading a book")

Input images can be passed for editing or style transfer:

model = Model('gemini-2.5-flash-image-preview')
pil_image = model.generate_image("Convert to Van Gogh style", images=source_image)

Async streaming

import asyncio

async def stream(model_name, prompt):
    model = Model(model_name)
    async for word in model.chat_async(prompt):
        print(word, end='')

asyncio.run(stream('sonar-pro', 'Give me 5 names for a juice bar'))

Prompt caching (Anthropic)

model = Model('claude-sonnet-4-6')
model.system_message = 'You are an experienced book analyzer'
model.cached_prompt = SOME_LONG_TEXT
response = model.chat('Who is the main character?', cached=False)

Agent

JustAI includes an Agent class for autonomous, tool-using agent execution. The agent runs in a loop: it reads a task file, calls tools as needed, and returns a final answer.

Basic agent usage

import asyncio
from justai import Agent, FileSystemTool

agent = Agent(
    model='claude-sonnet-4-6',
    role='Code reviewer',
    goal='Review Python files and report issues',
    tools=[FileSystemTool(read=['/path/to/src'])],
    max_iterations=10,
)

async def main():
    async for event in agent.run('tasks.md'):
        if event.type == 'response':
            print(event.content, end='')
        elif event.type == 'done':
            print(f'\nAnswer: {event.result.answer}')

asyncio.run(main())

Built-in tools

FileSystemTool — read/write files with path traversal protection:

FileSystemTool(read=['/allowed/read/dir'], write=['/allowed/write/dir'])

ShellTool — run shell commands with allowlist-based security:

ShellTool(allowlist=['echo', 'ls', 'python'])

WebFetchTool — fetch URLs with SSRF protection:

WebFetchTool()

Custom tools

@agent.tool
def search_database(ctx, query: str) -> str:
    """Search the database for matching records."""
    return db.search(query)

Dynamic instructions

@agent.instructions
def inject_context(ctx) -> str:
    return f'Current user: {ctx.deps["username"]}'

Skills

Load .md skill files to extend the agent's system prompt:

agent = Agent(
    model='claude-sonnet-4-6',
    role='Assistant',
    goal='Help with tasks',
    skills_dir='./skills',
)

Agent events

The agent.run() async generator yields AgentEvent objects with these types:

• status — status messages
• response — streamed text from the model
• tool_call — tool invocation (with name, arguments, tool_result)
• error — error messages
• done — final result with AgentResult (answer, audit trail, token usage, iterations)

License

MIT