Use with OpenAI

Prerequisites

Python
TypeScript

pip install prompty[jinja2,openai]

npm install @prompty/core @prompty/openai

You also need an OpenAI API key.

1. Write the `.prompty` File

Create chat.prompty:

---
name: openai-chat
description: Simple chat completion with OpenAI
model:
  id: gpt-4o-mini
  provider: openai
  apiType: chat
  connection:
    kind: key
    apiKey: ${env:OPENAI_API_KEY}
  options:
    temperature: 0.7
    maxOutputTokens: 1024
inputSchema:
  properties:
    - name: question
      kind: string
      default: What is Prompty?
template:
  format:
    kind: jinja2
  parser:
    kind: prompty
---
system:
You are a helpful assistant. Answer concisely.

user:
{{question}}

2. Run It

Python
TypeScript

import prompty

# One-liner: load → render → call LLM → return result
result = prompty.execute("chat.prompty", inputs={"question": "What is Prompty?"})
print(result)

For more control, use the pipeline stages individually:

import prompty

# Step 1 — Load the .prompty file → PromptAgent
agent = prompty.load("chat.prompty")

# Step 2 — Render template + parse role markers → list[Message]
messages = prompty.prepare(agent, inputs={"question": "Explain async/await"})

# Step 3 — Call OpenAI + process response → string
result = prompty.run(agent, messages)
print(result)

Async variant:

import asyncio
import prompty

async def main():
    result = await prompty.execute_async(
        "chat.prompty",
        inputs={"question": "What is Prompty?"},
    )
    print(result)

asyncio.run(main())

import { load, execute } from "@prompty/core";
import { OpenAIExecutor } from "@prompty/openai";

const result = await execute("chat.prompty", {
  inputs: { question: "What is Prompty?" },
});

console.log(result);

3. Switch Models

Change model.id in the frontmatter — no code changes needed:

model:
  id: gpt-4o          # GPT-4o (default, fast + capable)
  # id: gpt-4o-mini   # Cheaper, good for simple tasks
  # id: o1            # Reasoning model (higher latency)
  # id: gpt-4-turbo   # 128K context window

4. Environment Setup

Create a .env file in the same directory as your script:

OPENAI_API_KEY=sk-your-key-here

Prompty uses python-dotenv to load .env automatically. Make sure .env is in your .gitignore:

echo ".env" >> .gitignore

5. Tune Model Options

All options go under model.options: in the frontmatter:

model:
  id: gpt-4o-mini
  provider: openai
  connection:
    kind: key
    apiKey: ${env:OPENAI_API_KEY}
  options:
    temperature: 0.3        # Lower = more deterministic
    maxOutputTokens: 2048   # Max tokens in the response
    topP: 0.9               # Nucleus sampling
    frequencyPenalty: 0.2    # Reduce repetition
    presencePenalty: 0.1     # Encourage new topics
    seed: 42                 # Reproducible outputs
    stopSequences:           # Stop generation at these strings
      - "END"