Let ChatGPT compute Swiss taxes, affordability and mortgages with real data instead of estimating: the same engines as on grundheim.ch, with assumptions, warnings and sources.
ChatGPT already reads our pages when you ask about Swiss property topics. With the Grundheim connection it computes with our tools instead and answers with figures, assumptions and a link to the matching page.
Income and wealth tax for all 2,122 municipalities on the official ESTV tariffs, with marital status, children and pillar 3a. ChatGPT compares several municipalities side by side on request or finds the cheapest ones in a canton.
The stress test with the imputed interest rate, amortisation and running costs exactly as Swiss banks compute it: you give purchase price, equity and income, ChatGPT returns the ratio, the margin to the limit and the maximum affordable price.
The daily updated reference rates of 30 Swiss banks for SARON and fixed-rate mortgages from 2 to 15 years, including history. ChatGPT names the cheapest offers and places them on the yield curve.
Monthly costs with a tranche split, fixed or SARON under different rate worlds, prepayment penalties, forward mortgages and direct or indirect amortisation. Every answer includes a link that opens the calculator on grundheim.ch prefilled with your figures.
The rent-versus-buy comparison over your horizon, the pension-fund buy-in with the capital withdrawal tax of every canton, purchase costs and imputed rental value. ChatGPT runs the scenarios without you filling in forms.
Municipality profiles with tax multiplier, price level and noise, official sale prices, price trends and a verdict on whether an asking price sits above or below the local level. All tools are read-only; nothing is booked or sent.
Endpoint URL https://agent.grundheim.ch/mcp
https://chatgpt.com/plugins/plugin_asdk_app_6acb3c7ce3d8819188911ef4a4ce3818
Whether directory plugins are available depends on your ChatGPT plan, your region and any workspace policies. Without the directory, add the server in developer mode: Settings > Security and login > Developer mode, then choose "+" under Plugins and paste the endpoint URL.
The connection is anonymous: no Grundheim account is needed and we do not learn who is asking. The values you give your assistant are sent to our server for the calculation, processed in memory and not stored. We log only technical metadata (tool name, language, response time, client type). The conversation itself runs on the provider's platform and is subject to its privacy terms.
The full tool list, every connection path and the endpoint URL are on the technical reference page. We answer questions via the contact details in the imprint.
Does the connection cost anything?
No. The Grundheim server is open and needs no Grundheim account. You need a ChatGPT account in which directory plugins are available.
Where do the figures come from?
Taxes from the official ESTV tariffs, mortgage rates from the daily read reference rates of 30 banks, municipality data from federal and cantonal statistics, market prices from our own market monitoring. Every answer states its assumptions and the date of the reference rates.
Does Grundheim store my inputs?
No. The values are processed for the calculation only and not stored; we log technical metadata such as the tool name and the response time. Details are in section 12 of the privacy policy.
Is this financial advice?
No. The tools return reference figures under the usual rules of banks and authorities. Whether a bank finances you, and on what terms, is the bank's decision. The server cannot search property listings.
Claude is a trademark of Anthropic PBC, ChatGPT a trademark of OpenAI. Grundheim is not affiliated with or endorsed by either company; the names merely indicate compatibility.