Ask Claude or ChatGPT what you could borrow and it will guess. Connect this and it stops guessing — it runs the same sums our calculators run, built for Australian lending, and tells you where the answer came from. Free, no sign-up, about a minute to set up.
A general-purpose model knows a lot about mortgages and very little about Australian ones. It doesn’t know lenders test your repayments at about three percentage points above the rate you’d actually pay, and it rarely gets stamp duty right, because there are eight state scales and they move at budget time. These tools have all of that built in.
estimate_repayments
What would this loan cost me a month?
Monthly repayment, total repaid and total interest on a principal-and-interest loan.
estimate_borrowing_power
How much could I borrow?
Runs Australian income tax on your household income, takes off living costs and existing repayments, then tests what's left at the buffered rate lenders assess against.
estimate_refinance_savings
Is it worth switching?
Compares your current rate against a better one and shows the monthly and whole-of-term difference.
estimate_refinance_break_even
How long until switching pays for itself?
Counts the switching costs against the saving and returns the month you get ahead. This is the number that decides a refinance, and it's the one nobody quotes.
estimate_equity_and_lvr
How much equity can I actually use?
Not value minus balance — that's the figure you can't borrow. This returns the 80% number lenders release to, and how far off it you are if you're over.
estimate_stamp_duty
What's the duty on this place?
All eight states and territories, with the main first-home and owner-occupier concessions.
check_servicing
What would lenders actually lend me?
A real serviceability run across a panel of lenders, not our estimate. Per lender: how much, at what rate, and where the answer is no, why. The only one that counts HECS.
lookup_discharge_process
How do I leave my lender?
The discharge form your lender wants, where it goes, how long they say it takes and the fee where they publish one. Sixteen lenders, taken from their own pages.
https://www.arthr.com.au/api/mcp
If your assistant uses a config file instead of a settings screen, this is the entry:
{
"mcpServers": {
"arthr": {
"url": "https://www.arthr.com.au/api/mcp"
}
}
}No API key, no account, nothing to authorise. If you can’t find an MCP setting, your assistant doesn’t support it yet — the calculators on this site do the same maths.
For step-by-step instructions in a particular product, and what an agent can and can’t do about a mortgage, see connecting arthr to an AI agent.
It doesn’t ask who you are
The tools take figures — income, expenses, a HECS balance — and send an answer back. No name, no email, no phone, no account. We don’t store what you asked; we count how often each tool gets used so we know whether to keep running it. Starting an application is the one thing that needs to know you, and that’s separate.
An estimate isn’t an approval
The calculators use our own assumptions — borrowing power especially, where lenders apply their own expense benchmarks. Stamp duty leaves out pensioner, off-the-plan and foreign-buyer rules. Servicing is a real panel run rather than our maths, but it still isn’t an approval: a lender verifies income and identity before anything is decided.
The calculators don’t quote a rate
You tell them the rate to work with. Servicing is the exception — it returns what the panel assesses you at — but a rate you are actually offered still depends on the full picture, which is a conversation rather than a number.
Your assistant might still get it wrong
We can hand it the right numbers. We can’t control how it summarises them. If a figure matters, check it against the calculator page the answer links to.
Everything above works without an account, including the real lender servicing. Starting an application is the one thing that doesn’t, because it can end with a broker ringing you, and nobody should be able to arrange that on your behalf without you saying so.
So there is a second endpoint with one extra tool. You verify your mobile once and choose whether a broker may contact you. After that your assistant does the work — it already has your figures from the conversation, so you never type them in again.
https://www.arthr.com.au/api/mcp/advisor
Get a connection key at portal.arthr.com.au/connect, then:
claude mcp add --transport http arthr \ https://www.arthr.com.au/api/mcp/advisor \ --header "Authorization: Bearer <your key>"
It works for 90 days and only for arthr. You can disconnect an assistant any time, and it stops on the next thing it tries to do.
A way for an AI assistant to use someone else's tools. MCP stands for Model Context Protocol — an open standard that lets an assistant call a real calculator instead of working the answer out itself. Connect ours and when you ask about repayments or stamp duty, your assistant runs the same sums our calculators run and tells you the answer came from Arthr.
Because it will guess, and it will sound certain either way. Australian home lending has specifics a general model tends to miss: lenders test your repayments at about three percentage points above the rate you'd actually pay, and stamp duty runs on eight separate state scales that change at budget time. Our tools have those built in.
A little. You paste a URL into your assistant's settings, under connectors or MCP servers. That's the whole setup. If your assistant has no such setting, it doesn't support MCP yet and there's nothing to do — the calculators on this site do the same maths.
Nothing. It's free, there's no sign-up, and you don't give us an email to use it.
No. The tools take numbers, do the sum and send the answer back. We don't store what you asked, and we don't ask for your name, email or anything that identifies you. We count how often each tool is used so we know whether this is worth running, and that's the extent of it.
The same as the calculators on this site, because it's the same code. That means indicative, not exact. Borrowing power is a simplified model — lenders use their own expense benchmarks and assessment rules, so treat it as a starting point. Stamp duty uses current state scales but leaves out pensioner, off-the-plan and foreign-buyer rules.
Yes, and it's the point. The tools tell you roughly where you stand. A 1st Street broker (Credit Representative 490057, under Australian Credit Licence 389328) checks 40+ lenders and confirms the real numbers for your situation. Ask for a call back whenever you're ready.
An estimate tells you roughly where you stand. A broker tells you what you can actually get, and then goes and gets it.
Get an instant call backGeneral information only. The estimates these tools return are indicative and don’t take into account your objectives, financial situation or needs. They are not financial advice, credit advice, a credit assessment, a credit quote or an offer of credit. Arthr Pty Ltd provides marketing and lead-generation services. Mortgage broking and credit assistance are provided by 1st Street Pty Ltd trading as 1st Street Financial, Credit Representative 490057, authorised under Australian Credit Licence 389328.