How We Built an AI Shopping Deal Verifier with MCP & llms.txt

Most deal sites have the same flaw: a price is shown with no evidence behind it. A "$100 off" badge means nothing if the reference price is inflated, the price is from last week, or "in stock" was never actually checked. We built Savlume (https://savlume.com/) to fix that. Every deal carries its verification status, and the whole catalog is machine-readable, so AI agents can check a price instead of guessing one.

1. The problem: deal prices lie by omission

A deal is a claim — a price, a discount, availability — and a claim needs evidence and a timestamp. Three things go wrong on most deal sites: the reference price is inflated, so the discount looks bigger than it is; the price is stale but presented as current; stock and coupon conditions are asserted, never checked. Our rule from day one: if we can't show the evidence, we say so on the page.

2. Two-tier verification: retailer-verified vs source-reported

Every price on Savlume is one of two things: retailer-verified (confirmed at the retailer's own listing), or source-reported (the price comes from a deal source such as DealNews or 9to5Toys and has not been confirmed at the retailer — labeled exactly that on the page). A few more rules we enforce: expired and out-of-stock entries are kept as reference material, never as recommendations; listed/reference prices and conditional checkout prices are separate fields, and cashback, gift cards, and points are never subtracted from the checkout price; a failed check is not proof that an offer expired — we report "couldn't verify," not "deal dead"; historical comparisons only compare the same product, variant, and conditions, and missing information stays unknown.

A concrete example: our Black Friday air fryer guide (https://savlume.com/best/air-fryers-under-100) lists the Ninja Foodi 2-basket at $99.99 as source-reported via Target, while the Instant Pot Vortex Plus at $79.95 and the COSORI Pro III at $79.99 are retailer-verified on Amazon. Same page, different evidence levels, each labeled.

3. Making the catalog machine-readable: llms.txt + MCP

Verification is only half the job. The other half is letting machines read it: /llms.txt (https://savlume.com/llms.txt) is the index — about and methodology, today's deals, Black Friday and Cyber Monday pages, coupons, categories, stores, brands, reviews, and all 35 buying guides; /api/v1/items (https://savlume.com/api/v1/items?mode=all&limit=24) is JSON for every item, paginated, and each item page also has a /items/{id}/markdown text version and a /api/v1/items/{id} JSON representation; /feed/all.xml (https://savlume.com/feed/all.xml) is RSS for all updates; /api/mcp (https://savlume.com/api/mcp) is an MCP endpoint, so AI agents can query the catalog directly instead of scraping pages; /agent (https://savlume.com/agent) is the API guide for agents. The reasoning is simple: the same agents that write buying advice should be able to verify a price before quoting it. If an LLM can read our llms.txt, it can cite a real price with a real timestamp instead of hallucinating one.

4. How it was built

The site was built with the help of an AI coding agent (Codex), which made it fast to iterate on the data model and the verification labels. The 35 buying guides under /best (https://savlume.com/best) are structured content — multi-source review consensus plus current retailer offers — not scraped listicles. And the site says plainly on its llms.txt that it is "Independent US shopping summaries with AI assistance. Purchases take place at external retailers. No claim of personal product testing, exhaustive market coverage or guaranteed lowest price." That disclosure is a feature, not a disclaimer we hide.

5. Lessons so far

Label uncertainty on the page, not in a footnote nobody reads. A price without a time is a rumor — verification timestamps are part of the record. Don't subtract incentives from the price: cashback isn't a discount at checkout, so it never lowers the number we show. Ship the machine-readable layer early: llms.txt and the MCP endpoint cost little to add and make the site useful to the agents that increasingly do the shopping research.

Try it

Browse the deals: Savlume (https://savlume.com/). Read the machine-readable index: savlume.com/llms.txt (https://savlume.com/llms.txt). API guide for agents: savlume.com/agent (https://savlume.com/agent). Example buying guide: Top 5 Air Fryers Under $100 for Black Friday 2026 (https://savlume.com/best/air-fryers-under-100).