API and MCP reference

Check which JMAC programs fit

• API POST /api/v1/tools/check_scenario
• MCP tool jmac_check_scenario
• Read-only, uses the pricing engine

Checks a mortgage scenario against JMAC Lending's wholesale programs (non-QM, jumbo, closed-end seconds, and agency when loanType is agency) and returns which programs take it, why each fits, the room left, near misses with the limit they missed and the change that would fix them, and choices that open more programs. Use it when a mortgage professional asks which JMAC programs or loans fit a scenario, or whether JMAC can do a loan. It returns no rates, prices, fees or compensation. headline is a one-line answer; near misses may carry a fix the broker can check, which the tool never applies on its own. checkedAs says back how the scenario was read, with any assumed values (no prepay, one unit, investment occupancy for DSCR) marked. A missing field comes back as one question for the broker, with each field's choices; the tool never fills in the score, value, loan amount or documentation type. The tool takes numbers and choices only, never names, addresses or loan numbers.

Example

curl https://www.jmaclending.com/api/v1/tools/check_scenario \
  -H "Content-Type: application/json" \
  -d '{"lien":"first","purpose":"purchase","occupancy":"investment","propertyType":"sfr","state":"AZ","zip":"85016","value":640000,"loanAmount":480000,"fico":720,"docType":"dscr","dscr":1.1,"citizenship":"us","rental":"short"}'

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "jmac_check_scenario",
    "arguments": {
      "lien": "first",
      "purpose": "purchase",
      "occupancy": "investment",
      "propertyType": "sfr",
      "state": "AZ",
      "zip": "85016",
      "value": 640000,
      "loanAmount": 480000,
      "fico": 720,
      "docType": "dscr",
      "dscr": 1.1,
      "citizenship": "us",
      "rental": "short"
    }
  }
}

Inputs

Answer

Work out a rental's DSCR

• API POST /api/v1/tools/dscr_ratio
• MCP tool jmac_dscr_ratio
• Read-only, math only

Works out a rental property's debt service coverage ratio before an appraisal: estimated monthly rent over the monthly payment (principal and interest or interest only, plus taxes, insurance, HOA and flood), on both bases, with the costs used, the LTV, and the rent needed to reach a target ratio. Use it when a mortgage professional asks what DSCR a rental gives, or needs a DSCR for jmac_check_scenario. rate is the broker's own assumed note rate, never a JMAC rate. Taxes and insurance are dollars a year; HOA is dollars a month. The appraiser's rent schedule governs the final ratio.

Example

curl https://www.jmaclending.com/api/v1/tools/dscr_ratio \
  -H "Content-Type: application/json" \
  -d '{"purpose":"purchase","rent":3400,"price":640000,"loan":480000,"rate":7,"taxes":6240,"insurance":1680}'

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "jmac_dscr_ratio",
    "arguments": {
      "purpose": "purchase",
      "rent": 3400,
      "price": 640000,
      "loan": 480000,
      "rate": 7,
      "taxes": 6240,
      "insurance": 1680
    }
  }
}

Inputs

Answer

Errors

Over MCP, an error returns as a tool result with isError: true and the same error object.

Every answer, success or error, includes the notice and a terms object (version, url, privacy, privacyVersion), plus a Link header with the Terms and Privacy Policy links.

Limits

• Inputs accept numbers and choices only. Leave out names, addresses and loan numbers.
• Scenario checks: 5 a minute, 30 an hour and 50 a day from one network. Everyone using Claude.ai shares one allowance; everyone using ChatGPT shares another (30 a minute, 300 a day each). Those apps call from shared addresses. Days end at midnight Pacific.

Terms and support

By calling these tools you agree to JMAC's Terms of Use in effect when you call (jmaclending.com/terms-of-use), including Section 7A. Privacy: jmaclending.com/privacy-policy. Terms of use, Section 7A · Privacy · Questions: developers@jmaclending.com