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PAS2 requires API keys from both Mistral AI and OpenAI to function. This guide shows you how to obtain and configure these keys.

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Required API keys

PAS2 uses a dual-model architecture:
  • Mistral AI: For paraphrase generation and response generation (mistral-large-latest)
  • OpenAI: For hallucination detection judging (o3-mini)
Both API keys are required. PAS2 will raise a ValueError if either key is missing.

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Getting your Mistral AI API key

1

Create a Mistral AI account

Visit Mistral AI and sign up for an account.
2

Navigate to API keys

Go to your dashboard and find the API keys section.
3

Generate a new API key

Click “Create new key” and copy the generated key. Store it securely.
4

Set the environment variable

Add the key to your .env file:
HF_MISTRAL_API_KEY=your_mistral_api_key_here

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Getting your OpenAI API key

1

Create an OpenAI account

Visit OpenAI Platform and sign up for an account.
2

Navigate to API keys

Go to your account settings and select “API keys” from the menu.
3

Generate a new API key

Click “Create new secret key”, give it a name, and copy the key. This is your only chance to see the full key.
4

Set the environment variable

Add the key to your .env file:
HF_OPENAI_API_KEY=your_openai_api_key_here
OpenAI API keys are only shown once during creation. Store them securely in a password manager.

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Setting up environment variables

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Local development

Create a .env file in your project root:
.env
HF_MISTRAL_API_KEY=your_mistral_api_key_here
HF_OPENAI_API_KEY=your_openai_api_key_here
PAS2 automatically loads these variables using python-dotenv.

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Hugging Face Spaces deployment

1

Open your Space settings

Navigate to your Space on Hugging Face and click on “Settings”.
2

Add secrets

Scroll to the “Repository secrets” section.
3

Create secret variables

Add two new secrets:
  • Name: HF_MISTRAL_API_KEY, Value: your Mistral API key
  • Name: HF_OPENAI_API_KEY, Value: your OpenAI API key
4

Restart your Space

The Space will automatically restart and load the new secrets.
Never commit API keys to your repository. Always use environment variables or secrets management.

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Passing API keys programmatically

You can also pass API keys directly when initializing PAS2: 
from pas2 import PAS2

pas2 = PAS2(
    mistral_api_key="your_mistral_api_key",
    openai_api_key="your_openai_api_key"
)
This method takes priority over environment variables but is less secure for production use.

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Verifying API key configuration

Test your API key setup: 
from pas2 import PAS2
import os

try:
    # Try initializing with environment variables
    pas2 = PAS2(
        mistral_api_key=os.environ.get("HF_MISTRAL_API_KEY"),
        openai_api_key=os.environ.get("HF_OPENAI_API_KEY")
    )
    print("API keys configured successfully!")
except ValueError as e:
    print(f"Configuration error: {e}")

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Troubleshooting

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Missing API key errors

If you see: 
ValueError: Mistral API key is required. Set it via HF_MISTRAL_API_KEY...
Check that:
  • Your .env file exists and is in the correct location
  • The variable names are spelled correctly (HF_MISTRAL_API_KEY, HF_OPENAI_API_KEY)
  • There are no extra spaces or quotes around the keys

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API authentication errors

If you see authentication errors when making API calls:
  • Verify your API keys are valid and active
  • Check that you have available credits/quota on both platforms
  • Ensure the keys haven’t expired or been revoked

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API costs and rate limits

Be aware of API costs. Each query generates multiple API calls:
  • 1 call for paraphrase generation (Mistral)
  • N+1 calls for responses (Mistral, where N = number of paraphrases)
  • 1 call for hallucination judging (OpenAI)
Monitor your usage:

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Next steps

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