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Reference Implementation: LLM Prompt for Warranty Extraction

Purpose

Extract warranty-specific metadata from scanned receipts or warranty cards to ensure automated tracking of coverage periods and easier troubleshooting.

Prompt Template

You are an expert at analyzing household documents. Extract warranty information from the following text.

Text:
{{ocr_text}}

### Extraction Rules:
1. **Purchase Date**: Use the date of the receipt. If missing, use current date.
2. **Warranty Duration**: Look for phrases like "1 year warranty", "12 months", "Limited lifetime", etc.
3. **Manufacturer**: Identify the brand (e.g., Samsung, Dell, Bosch).
4. **Product Name**: Identify the specific model or product name.
5. **Expiration Date**: Calculate the expiration date based on the Purchase Date and Duration. Format: YYYY-MM-DD.

Return a JSON object:
{
  "product_name": "string",
  "manufacturer": "string",
  "purchase_date": "YYYY-MM-DD",
  "warranty_duration_months": integer,
  "expiration_date": "YYYY-MM-DD",
  "is_extended_warranty": boolean,
  "notes": "string (e.g., coverage details)"
}

JSON Schema for Constrained Output

{
  "type": "object",
  "properties": {
    "product_name": { "type": "string" },
    "manufacturer": { "type": "string" },
    "purchase_date": { "type": "string", "format": "date" },
    "warranty_duration_months": { "type": "integer" },
    "expiration_date": { "type": "string", "format": "date" },
    "is_extended_warranty": { "type": "boolean" },
    "notes": { "type": "string" }
  },
  "required": ["product_name", "manufacturer", "purchase_date", "expiration_date"]
}

n8n Workflow Integration Pattern

  1. Trigger: Paperless-ngx Webhook (Document Added with tag Admin/Warranty).
  2. OCR Pull: Fetch the full OCR text from the Paperless API.
  3. LLM Node: Use the prompt above with ollama or openai.
  4. Logic:
    • If expiration_date is found, calculate reminder date (e.g., expiration_date - 30 days).
  5. Target: Create a task in Vikunja or an event in Google Calendar titled "Warranty Expiring: [Product Name]".

  6. Tagging: Update the Paperless document metadata with the extracted product and manufacturer.

  7. Last reviewed: 2026-04-09

  8. Confidence: high

Sources / References