Apartment Loan API and MCP Server for Developers

Short answer

apartment.loans publishes a free REST API at /api/apartment-loan/{tool} and an MCP server at /mcp. Both run the same engine as the site's calculators: loan sizing by LTV, DSCR and debt yield, program comparison, cash-out, bridge takeout, break-even, maturity timelines and eligibility screening.

What you can call

The same math that runs the calculators on this site is open to developers and AI agents, free, with no key. Every response carries a disclaimer: results are estimates, not loan quotes.

Tool	What it returns	Required inputs
`size_loan`	Size an apartment loan the way a lender does: the lowest of the LTV, DSCR and debt-yield limits.	`value`, `noi`, `rate`
`compare_programs`	Max refinance loan under each agency program's published limits (Fannie Mae Small Loans, Freddie Mac Conventional Small, HUD 223(f)) plus a bank case.	`value`, `noi`, `rate`
`cash_out`	Net cash to the borrower from a cash-out refinance after payoff, prepayment, closing costs and reserves.	`value`, `noi`, `payoff`, `rate`
`bridge_takeout`	Test whether a bridge loan refinances into permanent debt at stabilization; returns surplus or shortfall, NOI needed and the highest workable rate.	`payoff`, `noi`, `rate`, `cap_rate`
`refinance_break_even`	Refinance now and pay the prepayment cost, or wait for the open window.	`balance`, `rate`, `months`, `prepay_pct`, `new_rate`
`maturity_timeline`	Dated refinance milestones working back from a loan maturity date.	`maturity`
`check_eligibility`	Screen a deal against published Fannie Mae Small Loans, Freddie Mac Conventional Small and HUD 223(f) criteria.	`units`, `loan`, `dscr`, `ltv`
`match_programs`	Rank loan programs for a deal with the reasons each fits or fails.	`units`, `occupancy`, `loan`

REST API

Call GET https://apartment.loans/api/apartment-loan/{tool}?input=value, or POST a JSON body to the same URL. GET https://apartment.loans/api/apartment-loan/ lists every tool with its full input schema. Rates are percents (6.25), DSCR is a multiple (1.25), LTV is a percent (75).

Example: https://apartment.loans/api/apartment-loan/size_loan?value=10000000&noi=600000&rate=6.25&max_ltv=75&min_dscr=1.25

MCP server

Connect any Model Context Protocol client to https://apartment.loans/mcp (streamable HTTP, stateless). It answers initialize, tools/list and tools/call with the tools above, so an assistant can size, compare and screen apartment loans with the same engine you see here.

Embed a calculator

Every calculator page has an Embed this calculator button that gives you an iframe snippet and a credit line. Embeds are free; please keep the credit link.

Embeddable calculators

Preview any of them before you paste the snippet:

Terms

Free for any use, including commercial, with attribution to apartment.loans. No warranty. Do not present results as a lender's quote. Program limits come from published Fannie Mae, Freddie Mac and HUD terms; see how we verify.

Frequently asked questions

Do I need an API key?

No. The REST endpoints and the MCP server are open and free. Responses are not cached and carry a disclaimer that results are estimates from apartment.loans, not a loan quote or commitment. Please attribute apartment.loans when you show the results to people.

Which loan programs does the API know about?

The compare_programs and check_eligibility tools apply the published limits for Fannie Mae Small Loans, Freddie Mac Conventional Small and HUD 223(f), plus a bank case you can adjust. The same limits drive the calculators on this site, so the API and the pages always agree.

How do I connect an AI assistant to the MCP server?

Add a remote MCP server in your client with the URL https://apartment.loans/mcp. It uses the streamable HTTP transport without sessions, so any client that supports remote servers can list and call the tools. The server describes each input, including units, in its tool schema.