Migrating from Altum

Based on Altum's public documentation, October 2026.

Using Claude Code? The migrate-from-altum skill moves your code over with these tables; see the Claude Code plugin.

Endpoints

Altum	What	Huispedia
`POST /avm`, `POST /v2/avm`	Home valuation	`GET /v5/properties/{locator}/valuation`
`POST /avm` with your own characteristics	Valuation with your own inputs	`POST /v5/valuations/scenarios`
`POST /avm/bulk`	Bulk valuation	`POST /v5/valuations/scenarios` Up to 100 homes per call, answered at once.
`POST /avmplus`	Home valuation plus	`GET /v5/properties/{locator}/valuation/plus` (contract)
`POST /v2/objectdata`	Property characteristics	`GET /v5/properties/{locator}`
`POST /interactive-reference`	Reference homes	`GET /v5/properties/{locator}/references` (contract)
`POST /v2/transaction`	Transactions	`GET /v5/properties/{locator}/transactions` (contract)
`POST /v2/transaction/ping`	Any transactions?	`HEAD /v5/properties/{locator}/transactions`
`POST /woz`, `GET /woz`	WOZ value	`GET /v5/properties/{locator}/woz`
`GET /market-trend`	Market trend	`GET /v5/areas/{area}/stats` `GET /v5/areas/{area}/trends`
`POST /location-data`	Location data	`GET /v5/addresses/{locator}` `GET /v5/areas/{area}/demographics`
`GET /autosuggest/v2`, `GET /autosearch`	Address search	`GET /v5/addresses/suggest`
`POST /condition-score/{img,url}`	Condition score	`GET /v5/properties/{locator}/condition` Per address; you do not send your own photos.
`GET /credit`	Usage	`GET /v5/account/usage`

Transactions, reference homes and home valuation plus come with a contract: [email protected].

Authentication

	Altum	Huispedia
Key	`x-api-key: <key>`	`X-API-Key: hp_…` or `Authorization: Bearer hp_…`
Base URL	`https://api.altum.ai`	`https://huispedia.dev/v5`
Method	`POST` with a JSON body	`GET` with the home in the path; `POST` only for scenarios
Testing	`/sandbox/` in the path	No sandbox: you test with your free credits or on the Endpoints page

Addresses and areas

Altum	Huispedia	Note
`postcode` + `housenumber` + `houseaddition`	`1076LJ-12-2`	Postcode, number and extension with hyphens in the path.
`houseaddition` (`A02`, `2B`)	`-A02`, `-2B`	Not sure: `GET /v5/addresses/1076LJ-12?all=true` returns every home with its `house_number_ext`.
`bag_id` (verblijfsobject)	`bag:0363200000028422` (nummeraanduiding)	The verblijfsobject id is `bag_verblijfsobject_id` in `GET /v5/addresses/{locator}`.
`valuationdate` (`20260901`)	`as_of_date` (`2026-09-01`)
`postcode` (Markttrend)	`neighbourhood:BU0363KH05`	An area is `level:code`; `GET /v5/areas/lookup?postcode=1076LJ` gives the codes.

Fields

Home valuation

POST /avm → GET /v5/properties/{locator}/valuation

Altum	Huispedia	Note
`postcode`, `housenumber`, `houseaddition`	`{locator}`
`valuationdate`	`?as_of_date=`	Up to six months back; further back with the valuation history.
`Output.PriceEstimation`	`valuation.value`	A number, not a string.
`Output.Confidence`	`valuation.lower`, `valuation.upper`, `valuation.interval`	There a 90% interval in one string; here an 80% interval in two numbers.
`Output.AccuracyIndicator`	`confidence.class`, `confidence.score_pct`, `confidence.within_10_pct`	There a class 0 to 7; here `high`, `medium` or `low` and percentages.
`Output.ValuationDate`	`valuation.as_of_date`
`Output.BagID`, `PostCode`, `HouseNumber`, `HouseAddition`, `Street`, `City`	`address.bag_id`, `address.postcode`, `address.house_number`, `address.house_number_ext`, `address.street`, `address.city`
`Output.Longitude`, `Latitude`	`address.location.lon`, `address.location.lat`
`Output.HouseType`, `BuildYear`, `InnerSurfaceArea`, `OuterSurfaceArea`, `Volume`, `EnergyLabel`	`type.house_type`, `construction.construction_year`, `dimensions.living_area_m2`, `dimensions.plot_area_m2`, `dimensions.volume_m3`, `energy.energy_label` In `GET /v5/properties/{locator}`	From Property characteristics.
`Output.Image`	Not available here

Valuation with your own characteristics

POST /avm → POST /v5/valuations/scenarios

Altum	Huispedia	Note
`postcode`, `housenumber`, `houseaddition`	`data[].postcode`, `data[].house_number`, `data[].house_number_ext`
`innersurfacearea`	`data[].living_area_m2`
`outersurfacearea`	`data[].plot_area_m2`
`buildyear`	`data[].construction_year`
`housetype`	`data[].house_type`	`terraced`, `corner`, `semi_detached`, `detached` or `apartment`.
`energylabel`	`data[].energy_label`
`Output.PriceEstimation`	`data[].valuation.value`

Property characteristics

POST /v2/objectdata → GET /v5/properties/{locator}

Altum	Huispedia	Note
`house_type_generic`, `house_type_specific`	`type.object_type`, `type.house_type_detail`
`inner_surface_area`, `outer_surface_area`, `volume`	`dimensions.living_area_m2`, `dimensions.plot_area_m2`, `dimensions.volume_m3`
`build_year`	`construction.construction_year`
`rooms`, `number_of_bathrooms`	`rooms.rooms`, `rooms.bathrooms`
`garden_orientation`, `garden_size`	`outdoor.garden_orientation`, `outdoor.garden_area_m2`
`monument`	`construction.is_monument`
`longitude`, `latitude`, `municipality_name`, `province`	`address.location.lon`, `address.location.lat`, `address.municipality`, `address.province`
`neighbourhood_code`, `municipality_code`	`neighbourhood.code`, `municipality_code` In `GET /v5/addresses/{locator}`
`ozb_tax`, `waste_tax_`, `sewage_tax_`	Not available here

Reference homes

POST /interactive-reference → GET /v5/properties/{locator}/references

Altum	Huispedia	Note
`reference_number`	`?limit=`	3 to 30.
`date_limit`	`?max_age_months=`
`housetype_to_search`, `strict_`, `comparable_`	`?same_type=`, `?max_distance_m=`, `?min_living_area_m2=`, `?max_living_area_m2=`, `?min_construction_year=`, `?max_construction_year=`	Bounds instead of levels.
`weight_*`	`?sort=`	Sort by `similarity`, `distance` or `date`; no weights of your own.
`GivenHouse`	`target`
`ReferenceHouses[]`	`data[]`
`Distance`, `Transactiondate`, `Source`	`data[].distance_m`, `data[].transaction_date`, `data[].source`
`TransactionPrice`, `IndexedTransactionPrice`	`data[].price`, `data[].price_indexed`
`InnerSurfaceArea`, `BuildYear`, `HouseType`	`data[].living_area_m2`, `data[].construction_year`, `data[].house_type`
`Weight`	Not available here
`VisualSimilarityScore`, `ReferencePriceMean`	Not available here

Transactions

POST /v2/transaction → GET /v5/properties/{locator}/transactions

Altum	Huispedia	Note
`valuation_date`	Not available here	You get every sale of the home; filter on `transaction_date` yourself.
`transaction`, `transaction_date`	`data[].transaction_id`, `data[].transaction_date`
`transaction_price`, `transaction_price_indexed`	`data[].price`, `data[].price_indexed`
`buyer`, `seller`, `family_transaction`, `more_real_estate`, `business_right`	Not available here

WOZ value

POST /woz → GET /v5/properties/{locator}/woz

Altum	Huispedia	Note
`index: 1`	`?index=`
`wozvalue[].Date`, `Value`, `IndexedValue`	`values[].reference_date`, `values[].value`, `values[].indexed_value`

Market trend

GET /market-trend → GET /v5/areas/{area}/stats

Altum	Huispedia	Note
`postcode`	`{area}`	Codes from `GET /v5/areas/lookup?postcode=`.
`averagePriceSingleFamilyHomes`, `averagePriceMultiFamilyHomes`	`market.avg_transaction_price`	Not split by home type.
`pricePerSquareMeterSingleFamily`, `pricePerSquareMeterMultiFamily`	`market.avg_transaction_price_per_m2`
`annualPriceChange`	`market.transaction_price_per_m2_yoy_pct`
`transactionData.totalSalesLast12Months`	`market.transactions_count`
`fiveYearPriceChange`	`data[].value`, `data[].yoy_pct` In `GET /v5/areas/{area}/trends`	Price per m² per month, five years back by default.

Errors

An error is application/problem+json with a fixed code; every code is on Errors.

Altum	Huispedia	Note
`400` (address not found)	`404 not_found`
`400` (date format, house type), `422` (validation)	`400 invalid_request`	`errors` names what is wrong per field.
`400` (no prediction possible)	`422 data_unavailable`
`401`, `403` (`Missing Authentication Token`)	`401 unauthenticated`
`403` (`Forbidden`, no access to the API)	`403 entitlement_required`
`429` (limit)	`429 rate_limited`	Wait `Retry-After` seconds.
`429` (quota)	`402 insufficient_credits`, `402 spend_cap_reached`
`500`	`500 internal_error`
`{"Output": "…"}`, `{"detail": […]}`	`application/problem+json` with `code`, `detail`, `errors`

Bulk and limits

	Altum	Huispedia
Rate	Fair use: up to 6 concurrent requests per second	6 per second and 6 at once on a paid plan; 1 and 2 on Free
Bulk	`POST /avm/bulk`, then fetch the job	`POST /v5/valuations/scenarios`: 100 homes per call, answered at once
Usage	`GET /credit`	`GET /v5/account/usage`

Altum

curl -X POST https://api.altum.ai/avm \
  -H "x-api-key: $ALTUM_KEY" \
  -H "Content-Type: application/json" \
  -d '{"postcode": "1076LJ", "housenumber": 12, "houseaddition": "2"}'

Huispedia

curl https://huispedia.dev/v5/properties/1076LJ-12-2/valuation \
  -H "X-API-Key: $HUISPEDIA_KEY"

Altum

import os, requests

r = requests.post(
    "https://api.altum.ai/avm",
    headers={"x-api-key": os.environ["ALTUM_KEY"]},
    json={"postcode": "1076LJ", "housenumber": 12, "houseaddition": "2"},
)
value = int(r.json()["Output"]["PriceEstimation"])

Huispedia

import os, requests

r = requests.get(
    "https://huispedia.dev/v5/properties/1076LJ-12-2/valuation",
    headers={"X-API-Key": os.environ["HUISPEDIA_KEY"]},
)
r.raise_for_status()
v = r.json()["valuation"]
value, lower, upper = v["value"], v["lower"], v["upper"]

Differences

Not available here

Photo with the valuation (image): not available here.
Pointing at a home by verblijfsobject id: not available here; use the nummeraanduiding.
A valuation more than six months back: not available here; the valuation history gives one value per month.
Your own weights, a weight per reference home and visual similarity: not available here; the order gives the likeness.
Buyer, seller and Kadaster codes with transactions: not available here.
Municipal charges (ozb_tax and the like): not available here.
Average WOZ per postcode (/woz/pc6): not available here.
Rental comparables, WWS points, rebuild and contents value: not available here.
NTA 8800 label calculation, sustainability, subsidies, roof scans, EPC: not available here; GET /v5/properties/{locator}/energy-label gives the registered label.
Move data, building geometry, photo labelling: not available here.

No equivalent at Altum

409 address_ambiguous with the candidates when an address has several homes: no equivalent at Altum.
What-if scenarios against the same base (scenarios): no equivalent at Altum.
Monthly valuation history in one call: no equivalent at Altum.
Environment (foundation, subsidence, noise, air) and amenities per address: no equivalent in Altum's public documentation.
A building with all its addresses (/v5/buildings/{bag_pand_id}): no equivalent in Altum's public documentation.

Sources

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