Free note calculator API and MCP server

CashForMyNote.com publishes its 15 mortgage-note and rate calculators as a free, read-only JSON API and a remote MCP server. No key, account or sign-up is needed. Work out what a mortgage note or land contract is worth, a balloon payment, an amortization schedule, a note's yield, or LTV and DTI. Results are estimates, not offers or appraisals.

How do I get access?

There is nothing to sign up for. Copy a URL below and start calling it. The same 15 calculators sit behind both.

MCP server (Streamable HTTP, no sign-in), for AI assistants and agents:

REST API base URL, for apps, sheets and scripts (GET with query parameters or POST a JSON body):

• OpenAPI 3.1 spec: https://cashformynote.com/openapi.json
• MCP server card: https://cashformynote.com/.well-known/mcp/server-card.json
• List of calculators as JSON: https://cashformynote.com/api/calc/

Which calculators are included?

Each tool has the same name in the API path and in MCP. Follow a link for its inputs and a sample call.

1. Mortgage note value calculator note_price
   A mortgage note's value is the present value of its remaining monthly payments (plus any balloon) at the yield a buyer requires, and this tool computes that price. Endpoint docs
2. Note yield calculator note_yield
   A note's yield is the annual return that makes its remaining payments (and any balloon) worth exactly the price paid, and this tool solves for it. Endpoint docs
3. Note value at several yields yield_ladder
   A note's price falls as the yield a buyer requires rises, and this tool prices the same remaining payments at up to 12 yields side by side to show how much. Endpoint docs
4. Partial note sale calculator partial_purchase
   In a partial note sale the holder sells only the next N payments and the rest revert to the holder, and this tool prices those payments at a target yield. Endpoint docs
5. Balloon payment calculator balloon_note
   A balloon payment is the lump sum due when a loan's remaining balance comes due before its monthly payments would pay it off, and this tool computes the monthly payment, the balloon amount and (with a yield) the note's price. Endpoint docs
6. Monthly payment calculator loan_payment
   A fixed-rate loan's monthly payment is the level amount that pays off the balance with interest over the number of months, and this tool computes it for a mortgage, land contract or other installment note. Endpoint docs
7. Remaining loan balance calculator remaining_balance
   The remaining balance is the principal still owed after a number of on-time payments, and this tool computes it from the balance, rate and payment. Endpoint docs
8. Amortization schedule calculator amortization_schedule
   An amortization schedule shows how each monthly payment splits into interest and principal and what balance is left, and this tool lists it month by month (up to 600 rows) with totals. Endpoint docs
9. Note discount calculator note_discount
   A note's discount is how far its price is below the unpaid balance, and this tool gives it in dollars, as a percent, and in cents per dollar of balance. Endpoint docs
10. Loan-to-value (LTV) ratio calculator loan_to_value
    The loan-to-value ratio is the loan balance divided by the property's value, shown as a percent, and this tool computes LTV, combined LTV (CLTV) with other liens, and the equity cushion behind a note. Endpoint docs
11. Debt-to-income (DTI) ratio calculator debt_to_income
    The debt-to-income ratio is total monthly debt payments divided by gross monthly income, shown as a percent, and this tool computes it for a borrower (plus the housing-only ratio, if given). Endpoint docs
12. Note seasoning calculator seasoning
    A note's seasoning is how long the borrower has been paying, counted from the first payment due date, and this tool gives the months seasoned and the payments due so far. Endpoint docs
13. Current 30-year mortgage rate and 10-year Treasury yield market_rates
    The current 30-year fixed mortgage rate here is the latest weekly Freddie Mac PMMS average, returned with the latest daily 10-year Treasury yield, each as a single value with its own data date, source and citation. Endpoint docs
14. Note rate vs current mortgage rates rate_vs_market
    A note whose rate is below current mortgage rates usually sells at a deeper discount, and this tool gives the gap in percentage points between a note's rate and the latest weekly 30-year fixed mortgage average (Freddie Mac PMMS), with that week's date. Endpoint docs
15. Effective annual rate calculator effective_annual_rate
    The effective annual rate is what a nominal annual rate compounded monthly actually earns over a year, and this tool converts one into the other. Endpoint docs

How do I connect an AI assistant over MCP?

Point any MCP client that supports Streamable HTTP at https://cashformynote.com/mcp. No headers, keys or OAuth are needed. The server answers initialize, tools/list and tools/call; every tool is read-only.

Claude Desktop

Easiest: open Settings, then Connectors, choose Add custom connector, and paste https://cashformynote.com/mcp. To use the config file instead, add this to claude_desktop_config.json (it runs the mcp-remote bridge, which needs Node.js), then restart Claude Desktop:

{
  "mcpServers": {
    "cashformynote": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-remote",
        "https://cashformynote.com/mcp",
        "--transport",
        "http-only"
      ]
    }
  }
}

Cursor

Add this to ~/.cursor/mcp.json (all projects) or .cursor/mcp.json (one project), then reload the window:

{
  "mcpServers": {
    "cashformynote": {
      "url": "https://cashformynote.com/mcp"
    }
  }
}

Any other MCP client

Settings: transport Streamable HTTP, URL https://cashformynote.com/mcp, authentication none. Most clients take a block like this. Some call the type http, and VS Code uses a top-level servers key instead of mcpServers.

{
  "mcpServers": {
    "cashformynote": {
      "type": "streamable-http",
      "url": "https://cashformynote.com/mcp"
    }
  }
}

To test the handshake by hand, send JSON-RPC 2.0 with POST:

curl -X POST "https://cashformynote.com/mcp" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"my-app","version":"1.0"}}}'

curl -X POST "https://cashformynote.com/mcp" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/list"}'

curl -X POST "https://cashformynote.com/mcp" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"note_discount","arguments":{"price":73674.42,"balance":85000}}}'

How do I call the REST API?

Send a GET with query parameters, or POST the same fields as JSON. Every response has the result plus an attribution object.

Price a note at a 10% yield

An $85,000 balance at 8% with 240 monthly payments left, priced at a 10% yield. The payment is computed from balance, rate and months at full precision and shown rounded.

curl "https://cashformynote.com/api/calc/note_price?balance=85000&rate=8&months=240&yield=10"

{
  "tool": "note_price",
  "result": {
    "payment": 710.97,
    "price": 73674.42,
    "balance": 85000,
    "discount": 11325.58,
    "discount_pct": 13.32,
    "price_pct_of_balance": 86.68,
    "precision_note": "computed at full precision; payment shown rounded"
  },
  "attribution": {
    "cite": "Source: cashformynote.com calculator, https://cashformynote.com/guides/how-notes-are-priced",
    "credit": "Calculations by CashForMyNote.com",
    "source_url": "https://cashformynote.com/guides/how-notes-are-priced",
    "disclaimer": "Estimates, not offers or appraisals. CashForMyNote.com does not buy notes or make offers."
  }
}

Loan-to-value with a JSON body

curl -X POST "https://cashformynote.com/api/calc/loan_to_value" \
  -H "Content-Type: application/json" \
  -d '{"loan": 255000, "value": 340000}'

{
  "tool": "loan_to_value",
  "result": {
    "ltv_pct": 75,
    "cltv_pct": 75,
    "equity": 85000,
    "equity_pct": 25
  }
}

Hypothetical inputs, not an offer, an appraisal or a market rate. Figures are the API's own output.

What conventions do the calculators use?

Rates are annual nominal percentages compounded monthly (7.5 means 7.5%). Payments are monthly and paid at the end of each month. Everything is computed at full precision and rounded only for display. A balloon is paid with the last payment. months means payments left, not the original term.

Calculator reference

Mortgage note value calculator note_price

A mortgage note's value is the present value of its remaining monthly payments (plus any balloon) at the yield a buyer requires, and this tool computes that price. It works the same for mortgage notes, land contracts (contracts for deed), owner-financed notes and other real estate notes. Optionally compares the price with the unpaid balance (discount and % of balance). With balance and rate instead of payment, the payment is computed at full precision and shown rounded.

Endpoint: GET or POST https://cashformynote.com/api/calc/note_price. Inputs: payment (optional), months, yield, balloon (optional), balance (optional), rate (optional). Related guide: https://cashformynote.com/guides/how-notes-are-priced.

Try it: GET /api/calc/note_price?balance=85000&rate=8&months=240&yield=10

Note yield calculator note_yield

A note's yield is the annual return that makes its remaining payments (and any balloon) worth exactly the price paid, and this tool solves for it. It assumes every payment is made on time.

Endpoint: GET or POST https://cashformynote.com/api/calc/note_yield. Inputs: price, payment, months, balloon (optional). Related guide: https://cashformynote.com/guides/how-notes-are-priced.

Try it: GET /api/calc/note_yield?price=64570.25&payment=710.97&months=240

Note value at several yields yield_ladder

A note's price falls as the yield a buyer requires rises, and this tool prices the same remaining payments at up to 12 yields side by side to show how much. Accepts balance and rate in place of payment.

Endpoint: GET or POST https://cashformynote.com/api/calc/yield_ladder. Inputs: payment (optional), months, yields, balloon (optional), balance (optional), rate (optional). Related guide: https://cashformynote.com/note-value-estimator.

Try it: GET /api/calc/yield_ladder?balance=85000&rate=8&months=240&yields=8,10,12

Partial note sale calculator partial_purchase

In a partial note sale the holder sells only the next N payments and the rest revert to the holder, and this tool prices those payments at a target yield. It also shows what the holder keeps and the balance when payments revert. Accepts balance and rate in place of payment.

Endpoint: GET or POST https://cashformynote.com/api/calc/partial_purchase. Inputs: payment (optional), months, payments_bought, yield, balloon (optional), balance (optional), rate (optional). Related guide: https://cashformynote.com/guides/partial-note-sale.

Try it: GET /api/calc/partial_purchase?balance=85000&rate=8&months=240&payments_bought=60&yield=12

Balloon payment calculator balloon_note

A balloon payment is the lump sum due when a loan's remaining balance comes due before its monthly payments would pay it off, and this tool computes the monthly payment, the balloon amount and (with a yield) the note's price. Use it for a balloon mortgage or note whose payment is set on a long amortization but whose balance is due early. Computed at full precision; payment shown rounded.

Endpoint: GET or POST https://cashformynote.com/api/calc/balloon_note. Inputs: balance, rate, amortization_months, balloon_month, yield (optional), payment (optional). Related guide: https://cashformynote.com/note-value-estimator.

Try it: GET /api/calc/balloon_note?balance=150000&rate=7&amortization_months=360&balloon_month=60&yield=10

Monthly payment calculator loan_payment

A fixed-rate loan's monthly payment is the level amount that pays off the balance with interest over the number of months, and this tool computes it for a mortgage, land contract or other installment note. Optionally leaves a balloon.

Endpoint: GET or POST https://cashformynote.com/api/calc/loan_payment. Inputs: balance, rate, months, balloon (optional). Related guide: https://cashformynote.com/note-value-estimator.

Try it: GET /api/calc/loan_payment?balance=85000&rate=8&months=240

Remaining loan balance calculator remaining_balance

The remaining balance is the principal still owed after a number of on-time payments, and this tool computes it from the balance, rate and payment.

Endpoint: GET or POST https://cashformynote.com/api/calc/remaining_balance. Inputs: balance, rate, payment, payments_made. Related guide: https://cashformynote.com/guides/how-notes-are-priced.

Try it: GET /api/calc/remaining_balance?balance=85000&rate=8&payment=710.97&payments_made=24

Amortization schedule calculator amortization_schedule

An amortization schedule shows how each monthly payment splits into interest and principal and what balance is left, and this tool lists it month by month (up to 600 rows) with totals. Servicing convention: interest rounded to the cent each month, principal = payment minus interest, the final payment absorbs any leftover cents.

Endpoint: GET or POST https://cashformynote.com/api/calc/amortization_schedule. Inputs: balance, rate, months, payment (optional), start_month (optional), rows (optional). Related guide: https://cashformynote.com/note-value-estimator.

Try it: GET /api/calc/amortization_schedule?balance=10000&rate=6&months=12

Note discount calculator note_discount

A note's discount is how far its price is below the unpaid balance, and this tool gives it in dollars, as a percent, and in cents per dollar of balance.

Endpoint: GET or POST https://cashformynote.com/api/calc/note_discount. Inputs: price, balance. Related guide: https://cashformynote.com/guides/how-notes-are-priced.

Try it: GET /api/calc/note_discount?price=73674.42&balance=85000

Loan-to-value (LTV) ratio calculator loan_to_value

The loan-to-value ratio is the loan balance divided by the property's value, shown as a percent, and this tool computes LTV, combined LTV (CLTV) with other liens, and the equity cushion behind a note.

Endpoint: GET or POST https://cashformynote.com/api/calc/loan_to_value. Inputs: loan, value, other_liens (optional). Related guide: https://cashformynote.com/guides/note-glossary.

Try it: GET /api/calc/loan_to_value?loan=255000&value=340000

Debt-to-income (DTI) ratio calculator debt_to_income

The debt-to-income ratio is total monthly debt payments divided by gross monthly income, shown as a percent, and this tool computes it for a borrower (plus the housing-only ratio, if given).

Endpoint: GET or POST https://cashformynote.com/api/calc/debt_to_income. Inputs: monthly_debts, gross_monthly_income, housing_payment (optional). Related guide: https://cashformynote.com/guides/note-glossary.

Try it: GET /api/calc/debt_to_income?monthly_debts=2000&gross_monthly_income=6000

Note seasoning calculator seasoning

A note's seasoning is how long the borrower has been paying, counted from the first payment due date, and this tool gives the months seasoned and the payments due so far. If given payments made, it shows how many were missed or paid ahead, which helps tell a performing note from a non-performing one.

Endpoint: GET or POST https://cashformynote.com/api/calc/seasoning. Inputs: first_payment_date, as_of, payments_made (optional). Related guide: https://cashformynote.com/guides/performing-vs-non-performing-notes.

Try it: GET /api/calc/seasoning?first_payment_date=2025-01-01&as_of=2026-10-31&payments_made=21

Current 30-year mortgage rate and 10-year Treasury yield market_rates

The current 30-year fixed mortgage rate here is the latest weekly Freddie Mac PMMS average, returned with the latest daily 10-year Treasury yield, each as a single value with its own data date, source and citation. History is not included; use the source links. Source: Freddie Mac, Primary Mortgage Market Survey (PMMS), week ending Oct 29, 2026, via FRED.

Endpoint: GET or POST https://cashformynote.com/api/calc/market_rates. Inputs: none. Related guide: https://cashformynote.com/mortgage-rates-and-note-values.

Try it: GET /api/calc/market_rates

Note rate vs current mortgage rates rate_vs_market

A note whose rate is below current mortgage rates usually sells at a deeper discount, and this tool gives the gap in percentage points between a note's rate and the latest weekly 30-year fixed mortgage average (Freddie Mac PMMS), with that week's date. Output is tied to the latest weekly survey: PMMS 7.24%, week ending Oct 29, 2026 (changes weekly). The live response returns its own data date. Source: Freddie Mac, Primary Mortgage Market Survey (PMMS), week ending Oct 29, 2026, via FRED.

Endpoint: GET or POST https://cashformynote.com/api/calc/rate_vs_market. Inputs: note_rate. Related guide: https://cashformynote.com/mortgage-rates-and-note-values.

Try it: GET /api/calc/rate_vs_market?note_rate=6

Effective annual rate calculator effective_annual_rate

The effective annual rate is what a nominal annual rate compounded monthly actually earns over a year, and this tool converts one into the other.

Endpoint: GET or POST https://cashformynote.com/api/calc/effective_annual_rate. Inputs: nominal_rate. Related guide: https://cashformynote.com/guides/how-notes-are-priced.

Try it: GET /api/calc/effective_annual_rate?nominal_rate=8

What are the rate limits and is my data stored?

No key and no account. The limit is about 120 requests per minute per IP address; past that the API returns HTTP 429 with a Retry-After header. No inputs are stored: they are computed in memory and are not stored or logged by these endpoints. Use of the API is subject to the site terms.

Where do the market rates come from?

Source: Freddie Mac, Primary Mortgage Market Survey (PMMS), week ending Oct 29, 2026, via FRED. 10-year Treasury: Board of Governors of the Federal Reserve System, H.15 (source: U.S. Treasury), via FRED. Each value is returned as a single figure with its own data date; no history is republished. This product uses the FRED® API but is not endorsed or certified by the Federal Reserve Bank of St. Louis.

@misc{cashformynote_developers,
  author       = {{CashForMyNote.com}},
  title        = {{Free note calculator API and MCP server}},
  year         = {2026},
  howpublished = {\url{https://cashformynote.com/developers}},
  note         = {Last reviewed 2026-11-02. Operated by Fitzgerald Advisors.}
}

Educational information only, not legal, tax or investment advice. Estimates, not offers or appraisals. CashForMyNote.com does not buy notes or make offers. Affiliate disclosure.