Summitly for developers
Canadian home-buying calculators and pre-construction data, by API
The short answer
Summitly's developer API gives you the same Canadian home-buying calculators that run on Summitly.ca, free with an API key, and paid access to the Summitly Pre-Construction Pipeline dataset. Every response is JSON over HTTPS, authenticated with a Bearer key.
Your account
Keys, usage and plan
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Reference
API reference
https://www.summitly.ca/api/developer/v1. Machine-readable: OpenAPI 3.1.Authentication
curl -H "Authorization: Bearer smt_live_..." \
"https://www.summitly.ca/api/developer/v1/calculators/land-transfer-tax?price=950000&toronto=true&firstTimeBuyer=true"Calculators (every plan)
GET with query parameters or POST with a JSON body to /calculators/{name}. The maths is the same as the calculators on Summitly.ca, with Ontario and federal rules dated and sourced in every response.
| Name | Inputs | On Summitly.ca |
|---|---|---|
| mortgage | price, downPayment, ratePct, amortizationYears, frequency, termYears | Mortgage payment calculator |
| affordability | annualIncome, monthlyDebts, downPayment, ratePct, amortizationYears, propertyTaxRatePct, condoFeesMonthly | Home affordability calculator |
| land-transfer-tax | price, toronto, firstTimeBuyer | Ontario land transfer tax calculator |
| cmhc | price, downPayment, amortizationYears, firstTimeOrNewBuild | CMHC insurance calculator |
| closing-costs | price, downPayment, toronto, firstTimeBuyer, legal, inspection | Closing costs calculator |
| rent-vs-buy | homePrice, downPaymentPercent, monthlyRent, mortgageRate, amortization, annualRentIncrease, homeAppreciation, investmentReturn, annualPropertyTax, annualInsurance, annualMaintenance, closingCosts, years | Rent vs buy calculator |
| fhsa-hbp | buyers, fhsaBalance, rrspBalance, otherSavings | FHSA and Home Buyers' Plan calculator |
Pre-construction pipeline
/aggregates and /ask?q= (every plan), /projects and /projects/{id} (Starter and up), /projects/{id}/history (Pro and up), /exports/projects?format=csv|geojson|parquet (CSV from Starter, GeoJSON from Pro, Parquet on Business), /changes?since= (Business). Filters: city, region, province, segment (low-rise, condo, rental, mixed-use), status, type, min_storeys, max_storeys, min_units, recorded_since, updated_since, bbox=minLat,minLng,maxLat,maxLng, cursor, limit (up to 100). Every response has meta.attribution; keep it with the data. Change kinds: created, status, units, storeys, unpublished. About the dataset
Webhooks
Business plans can receive the change feed by POST. Each delivery has a Summitly-Signature: t=<unix>,v1=<hex> header: the HMAC-SHA256 of <t>.<raw body> with your webhook secret. Reply 2xx within 10 seconds; after 10 failed deliveries in a row the webhook is turned off.
import crypto from "node:crypto";
const [t, v1] = header.split(",").map((p) => p.split("=")[1]);
const expected = crypto.createHmac("sha256", secret).update(`${t}.${rawBody}`).digest("hex");
const ok = crypto.timingSafeEqual(Buffer.from(expected), Buffer.from(v1));Errors
| 401 missing_key / invalid_key | No key, a malformed key, or a revoked key. |
|---|---|
| 403 plan_required / city_not_in_plan / choose_city | The endpoint or city is not in your plan. |
| 422 invalid_input | Calculator input failed validation; `issues` lists each field. |
| 429 rate_limited / daily_quota / monthly_quota | Slow down, or upgrade for a higher quota. |
| 503 not_ready | The API is being switched on. Retry later. |
More ways in
Questions
Developer questions
Is the Summitly API free?
The free plan includes every calculator endpoint, monthly totals for one city, the map explorer and one area alert, up to 1,000 calls a month. Project records start on Starter; the daily change feed, webhooks and Parquet exports are on Business.
Does the API include MLS® listings?
No. Real estate board rules do not let us redistribute MLS® listing data, so the API has none: no active, sold or leased listings. To search listings, link your users to Summitly.ca.
How do I authenticate?
Create a key in the dashboard on this page and send it as `Authorization: Bearer smt_live_…` (or an `X-Api-Key` header). Keys are shown once; revoke and replace one any time.
What are the rate limits?
Per key: 20 requests a minute on Free, 60 on Starter, 120 on Pro and 240 on Business, plus a per-address limit. Monthly quotas are counted in UTC; paid plans can turn on overage instead of stopping. A 429 response says which limit you hit.
Can AI assistants use Summitly?
Yes. Summitly runs a read-only MCP server and publishes an OpenAPI description, so assistants can use the calculators and guides and send people to Summitly.ca to search, book a tour or talk to an agent.
