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The Letter Generator API uses API key authentication to secure your requests. You must include your API key in the header of every API request.

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Get your API key

To obtain your API key:
  1. Sign up for an account at lettergenerator.co
  2. Log in to your dashboard
  3. Navigate to Settings > API Keys
  4. Click Generate New API Key
  5. Copy and securely store your API key
Keep your API key secret and never share it publicly or commit it to version control. Treat it like a password.

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Authentication method

Include your API key in the Authorization header of every request using the Bearer token format: 
Authorization: Bearer YOUR_API_KEY

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Example request

Here’s how to authenticate a request to the Letter Generator API: 
curl https://api.lettergenerator.co/v1/generate \
  -H "Authorization: Bearer lg_sk_1234567890abcdef" \
  -H "Content-Type: application/json" \
  -X POST \
  -d '{
    "type": "cover_letter",
    "tone": "professional",
    "recipientName": "Sarah Johnson",
    "purpose": "Software Engineer position at TechCorp",
    "details": "5 years of experience in full-stack development"
  }'

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Managing API keys

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Rotate keys regularly

For security best practices, rotate your API keys periodically:
  1. Generate a new API key in your dashboard
  2. Update your application to use the new key
  3. Test that the new key works correctly
  4. Delete the old API key

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Multiple API keys

You can create multiple API keys for different applications or environments:
  • Development - Use a separate key for testing
  • Production - Use a dedicated key for your live application
  • Team members - Issue individual keys for tracking and revocation

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Revoke compromised keys

If your API key is compromised:
  1. Immediately delete the compromised key from your dashboard
  2. Generate a new API key
  3. Update all applications using the old key
  4. Monitor your usage logs for suspicious activity

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Authentication errors

You may encounter these authentication errors:
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401 Unauthorized
error
Your API key is missing, invalid, or expired. Verify that you’re including the correct key in the Authorization header.
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403 Forbidden
error
Your API key is valid but doesn’t have permission to access this resource. Check your plan limits.

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Example error response

{
  "error": {
    "code": "invalid_api_key",
    "message": "The API key provided is invalid or has been revoked",
    "type": "authentication_error"
  }
}

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Best practices

Use environment variables or secure credential management systems to store your API keys. Never hardcode keys in your source code.
# .env file
LETTER_GENERATOR_API_KEY=lg_sk_1234567890abcdef
Always make API requests over HTTPS to encrypt your API key in transit. HTTP requests will be rejected.
Regularly check your API usage in the dashboard to detect unauthorized access or unusual patterns.
Handle authentication errors gracefully in your application and log failures for debugging.

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