TransparentYou have probably heard the word "API" and nodded along without anyone ever explaining it. Here is the plain version, using our own free car API for Portugal as the example — no computer-science degree required.
What an API actually is
Think of a restaurant. You sit at a table (your website, your spreadsheet, an app on your phone). You do not walk into the kitchen and cook — you tell the waiter what you want, and the waiter brings it back from the kitchen. An API is that waiter. It is one program politely asking another program for something and getting a tidy answer back, automatically, with nobody copying and pasting by hand.
So when we say "the TransparentCars API", we mean this: our systems can hand car data straight to your systems. You ask "what is a fair price for a 2015 Renault Clio with 118,000 km?" and you get a number back in a fraction of a second — the same number our own website uses.
What the free TransparentCars API gives you in Portugal
TransparentCars is a local Portuguese used-car seller. We built our website on top of a small, honest data service, and we opened that same service to everyone. It is free, and it needs no key — no sign-up, no token, no invoice. You just call it. Here is what it can tell you:
- A fair price for a car. Give it a make, model, year and mileage and it returns a fair-price range — low, middle and high — built from comparable cars on sale in Portugal right now. This is the same engine behind our fair price tool. It answers one question honestly: is this asking price reasonable, or not?
- Annual road tax and running cost. Give it engine size, CO₂, fuel and the year of first registration and it returns the yearly IUC road tax in euros — what the car costs just to keep it legally on the road. Electric cars come back as exempt. It is the same maths as our public road-tax calculator.
- The used-car catalogue. The cars we actually have for sale — make, model, year, mileage, price, photos — the same listings you see on the site, available as clean data you can pull into your own page or sheet.
- The list of makes and models the fair-price tool understands, so you always ask with the right spelling.
Every answer is plain numbers or public listing data — no personal information involved.
Who would actually want this, and why
Two everyday examples make it concrete.
A small local dealer. Say you run a little stand with fifteen cars. You could show a small "fair price" badge on each listing — "priced within the fair range for Portugal" — pulled live from our valuation data. It tells a nervous buyer, in one glance, that you are not pricing on a whim. You do not need a big IT department; one developer wires it up once.
A blogger, accountant or small-business owner. Maybe you write about cars, or you help clients budget for one. Instead of looking up road tax by hand for twenty different cars, you can have the numbers flow straight into a spreadsheet. Ask once, and the yearly IUC for each car fills itself in. Same for a fair-price column next to a list of cars you are comparing.
Do you need to be a programmer? The no-code angle
Mostly, yes — someone technical connects it the first time — but not always. Modern spreadsheets (Google Sheets, for instance) can pull data straight from a web address, so a careful non-programmer can drop a road-tax or fair-price figure into a cell without writing real code. We do not yet offer a drop-in "paste this box on your site" widget; if that is what you need, the honest answer today is that a developer spends an hour, not a week. If you would rather we handled the fair-price side for you, the simplest route is to sell your car or list with us directly.
The technical bits, kept short
For the developer you eventually hand this to: there is a full developer API page with a machine-readable OpenAPI description at transparent.pt/openapi.yaml, so their tools can understand every endpoint automatically. The addresses look like transparent.pt/api/public/valuation and transparent.pt/api/public/cars. The code is open-source on GitHub (the api and mcp repositories under transparentpt). There is a generous per-visitor fair-use limit — plenty for a normal site or spreadsheet — and if you go over it, the service simply asks you to wait a moment. If you would rather your tools or an AI assistant talk to us conversationally, we also run an MCP server — that is a separate story, told in our MCP article.
The honest small print
We are not a neutral utility pretending to have no stake in the game. TransparentCars sells used cars in Portugal, and this free API runs on the same data we use ourselves. It is free to use under a Creative Commons licence, which simply asks that you credit "TransparentCars" as the source wherever you show the numbers. The fair-price range is built from real asking prices, not an official appraisal, and the road-tax figure is a well-maintained estimate for planning — not a bill from the tax office. Use it to make a sensible decision, not to win a court case.
Common questions
Is the TransparentCars API really free, with no key?
Yes. No account, no API key, no cost. You (or your developer) call the web address and get JSON back. The only limit is a fair-use cap per visitor so nobody can hammer it — normal use never gets near it.
Do I need to credit TransparentCars?
Wherever you display our numbers, yes — a simple "source: TransparentCars" is enough, as the Creative Commons licence asks. It keeps things honest for the people reading your page.
Is the data accurate enough to trust?
It is the same data our own Portuguese site runs on, so we have every reason to keep it right. Treat the fair-price range as a well-informed guide and the road tax as a solid estimate for budgeting, not as an official valuation or tax assessment.