22 May 2025 · 6 min read
AI document comparison is powerful but not magic. Here's a transparent look at how it works and where its limits are.
AI document comparison has become genuinely useful over the last two years. But there's a lot of marketing around AI capabilities that sets unrealistic expectations. This post explains honestly how AI reads vendor documents, where it excels, and where you still need human judgment.
When you upload a PDF or Word document to OfferInbox, the document's text content is extracted and sent to the Google Gemini API. The AI is given a structured prompt that asks it to extract specific fields: price, quantity, delivery terms, warranty, payment terms, exclusions, and so on.
The AI reads the entire document and returns a structured JSON response with the extracted data. This data is then stored and displayed in the comparison table. For image files (photos of quotes), the image itself is sent to the AI for processing.
AI is excellent at reading structured documents with clear tables and labeled fields. A professional PDF quote with a clear line-item table will be extracted with very high accuracy. AI is also good at reading dense text and finding relevant information that a human reader scanning quickly might miss — warranty conditions buried in footnotes, exclusions listed in small print, payment terms in the terms and conditions section.
AI accuracy drops with poorly formatted documents: handwritten quotes, blurry photos, documents with complex layouts where columns and rows are visually ambiguous. AI also struggles with highly domain-specific abbreviations it hasn’t encountered in context.
AI does not verify information against external sources. If a vendor quotes a material price that is 3x the market rate, the AI will extract the price but will not flag it as suspicious unless there is explicit comparison context.
AI outputs in OfferInbox are decision support, not final decisions. Before committing to a vendor based on the comparison table, verify key numbers against the original documents. This is especially important for high-value decisions.
The AI is removing 80-90% of the manual work. The remaining 10-20% — judgment, verification, context — is yours. That's the right division of labour.
OfferInbox does not store or use your documents to train AI models. The Google Gemini API processes your documents under terms that prohibit using API data for model training. Your documents are processed and then the extracted data is stored; the raw API interaction data is not retained for training purposes.
Ready to compare your vendor offers?
Start for free →