Property check
The due-diligence protocol for a listing: what the 35 checks are, which sources they use, how facts are kept apart from the AI's opinion, what it costs, and what the Chrome extension reads.
Last updated: September 16, 2026
Property check turns a listing into a structured protocol before you decide to buy. You paste the listing text, or the Chrome extension reads the page you have open, and the check runs 35 questions across the listing, public registers, map layers and your own budget. It is available without an account at /property-check and, with an account, from the dashboard.
How a check runs
- Extraction. A model (Claude Haiku) turns the listing text into structured facts: price, area, type, address, energy class, ownership, and so on. The server never fetches the listing page itself; the text comes from you or from the extension.
- Location. The address is geocoded once through OpenStreetMap. If you provide the exact address yourself, map checks unlock that the listing text alone could not.
- Five phases of checks. Phase 1 computes from the listing and your inputs. Phase 2 asks official registers. Phase 3 asks map layers at the point. Phase 4, the title deed, has no automated source yet and is shown as a gap with a link to the registry. Phase 5 asks the national zoning geoportal.
- Verdict. Three lines above the protocol: the most serious finding, the largest impact on your money, the largest gap. They are assembled from the statuses of the checks, not written by a model, so the same protocol always gives the same verdict. Above a protocol with gaps, “all clear” never appears.
- Assessment, optional. A second model (Claude Sonnet) writes an opinion based only on the facts in the protocol. It is shown as a separate layer, labelled as the model’s view, and it never looks anything up on its own.
The 35 checks
Price (9): price per m², gross and net rental yield, cash-on-cash return, value in 10 years at your assumed growth, what the energy class does to the price, price change since your last check, distance between asking prices and actually paid prices in the district, asking price versus real sale prices in the district, asking price versus the average price of farmland.
Financing (9): mortgage payment at the current market rate, fit with your income and obligations, does the rent cover the payment, total monthly cost of ownership, stress test at a rate 2 points higher, owning versus your current rent, limits the bank will apply, what is left of your budget after buying.
Legal (5): type of ownership and financing, parcel in the cadastre (area and land type), seller in the insolvency register, title deed liens and easements (phase 4, gap), zoning plan designation of the plot.
Building (2): estimated energy costs from the energy label, soil quality and protection class (BPEJ).
Owners’ association (3): identification in the public register, financial statements and repair fund, repair fund against the usual level.
Location (6): municipality population trend, amenities and accessibility, flood zone, radon index, noise, registered landslides.
Tax (1): holding-period test for a future sale, using the rule of the property’s country.
”What is left after buying”
One check uses data no listing tool has: your own income, expenses, loan payments and reserve from your Assetli profile. Your current housing cost is subtracted, because you will stop paying it. A missing item is not treated as zero; the check returns as locked until you fill it in, and the recalculation after you do is free and does not call a model.
Honesty rules
- No legal conclusions. The protocol says “according to the zoning plan valid from …, the parcel lies in area NS; verify with the building authority”, never “you can build here”. Legal facts are attributed to the authority with a source link and a date.
- Facts and opinion never mix. Register results and the model’s assessment are separate layers in the data and on the screen.
- A gap says why. Every unanswered check states whether we have no source for it or whether it is waiting for your input. Most gaps are the second kind.
- Nothing is fetched from listing portals. Scraping is prohibited by their terms; the text is yours to paste or for the extension to read in your own browser.
- Outside Czechia the Czech layers stay silent. Checks that read from the listing, OpenStreetMap, Wikidata, market energy prices and holding-period rules work anywhere; cadastre, floods, geology, zoning, insolvency and price benchmarks are Czech and are not run for a foreign address. A silent check is shown as a gap, never as “outside the flood zone”.
Cost and limits
| Without an account | With an account | |
|---|---|---|
| Checks | 3 per 24 hours, a global daily cap applies to all anonymous checks together | Unlimited, charged from your AI credit |
| Protocol from registers and maps | Yes | Yes |
| AI assessment | No | Yes, about 1.49 CZK from AI credit for extraction and assessment together |
| Reading a scanned zoning plan | No | About 17 CZK, confirmed separately before it runs |
| Filling in a missing value and recalculating | Yes, free | Yes, free |
| Saved to your account, price history, comparison | No | Yes |
| Listing text length | Up to 8 000 characters |
The price of a step is shown before you click it. Anonymous results are cached for 7 days by a fingerprint of the text.
The Chrome extension
The extension reads the page only after you click its icon, and only the active tab. It takes the visible text, the page title, the og:title and og:description tags, the breadcrumb navigation, the page address and, when the page publishes them next to a city name that matches the listing, the coordinates. Coordinates without a matching city are ignored, because portals also publish the agent’s office location.
It sends the result only to assetli.app, to the same endpoints the web uses. It does not track browsing, it does not read other tabs, and it cannot enter a birth number; the insolvency check works with a name and date of birth or a company ID.
Sources
ČÚZK (RÚIAN, cadastre), SPÚ (BPEJ soil classes), ČGS (radon, landslides), HEIS VÚV (declared flood zones), IPR Praha (noise), NGÚP (zoning plans), ARES (owners’ associations and companies), ISIR (insolvency register), OpenStreetMap (geocoding, amenities), Wikidata (municipalities), and pre-downloaded tables of real sale prices and farmland prices from official statistics. Each result in the protocol names its source and the date of the data.
What it is not
Not a valuation, not legal advice, and not a substitute for reading the title deed. It is a checklist that tells you what is known, what is not, and where to look.