callido rates — Dutch mortgage rates, read from the source

How it started

What does a Dutch mortgage actually cost today? It sounds like a question with an answer. It is not. Every lender publishes its own rate sheet — a PDF, in its own layout, on its own schedule, using its own names for the same thing. The comparison sites solve that by hand, or by approximation. We wanted the real numbers, from the source, every day.

What it does

callido rates reads the rate sheets the lenders publish themselves. 57 lenders — 43 mortgage providers and 14 savings providers — checked every day. 818 products. Around 372,000 individual rate entries, each one tied to the archived document it was read from, with its date and its source URL. Ask it for a comparison and you can always walk back to the PDF the number came from.

The hard part was meaning, not parsing

A rate sheet is full of things that look like prices and are not. A discount on a green loan part is not a green rate. A surcharge is not a product. One lender’s market-value class is another’s LTV band. So the system models the difference explicitly: discounts and surcharges are typed as what they are, products are classified, and the classifier watches itself — it reports drift when a lender changes its layout, records correctness findings, and cross-checks its own output against reference sources.

How it is used

A REST API, and an MCP server on top of it, so an AI assistant can ask about Dutch mortgage rates in plain language and get an answer that cites the rate sheet behind it.