For agents & developers

Underwriting API

The same multifamily math behind our free calculators, available as JSON. No API key, no account, no rate-limit tier. Every endpoint is a pure function of its query string — same input, same answer, no state stored.

Endpoints

All endpoints accept GET and return JSON. Percentages are passed as percents, so 6.5 means 6.5%.

Response shape

Every calculation echoes the inputs it used, so a result is self-describing even when defaults filled in the gaps.

{
  "inputs":  { "capRate": 6.5, "price": 8000000 },
  "result":  { "noi": 520000, "noiMonthly": 43333.33 },
  "formula": "NOI = cap rate × purchase price",
  "disclaimer": "Quick screen only — not investment, tax, or legal advice."
}

A value that cannot be computed — a cap rate with no price, an IRR that cannot be bracketed — comes back as null rather than zero, so it is never mistaken for a real answer.

Errors

A missing, non-numeric, or out-of-range parameter returns 400 with a message naming the field at fault.

{
  "error": "bad_request",
  "message": "Missing required parameter \"capRate\"."
}

Using this from an agent

We publish a skill describing how to screen a deal with these endpoints, including how to read the output and which assumptions to disclose.

Limits and honesty