> For the complete documentation index, see [llms.txt](https://docs.matrixian.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.matrixian.com/waarderen-en-taxeren/koopsom-api.md).

# Koopsom API

## GET /mx-transaction-finder

> Conveniently retrieve residential transaction data for a specific object.

```json
{"openapi":"3.1.1","info":{"title":"Matrixian API","version":"1.0.0"},"servers":[{"url":"https://api.matrixian.com/v1","description":"Matrixian API"}],"security":[{"BearerAuth":[]}],"components":{"securitySchemes":{"BearerAuth":{"type":"http","scheme":"bearer","bearerFormat":"{{API_KEY}}"}},"schemas":{"TransactionFinderInput":{"properties":{"postalCode":{"type":"string","title":"Postalcode","description":"Postal code"},"houseNumber":{"type":"integer","title":"Housenumber","description":"House number"},"houseLetter":{"anyOf":[{"type":"string"},{"type":"null"}],"title":"Houseletter","description":"House letter"},"houseNumberExt":{"anyOf":[{"type":"string"},{"type":"null"}],"title":"Housenumberext","description":"House number extension"},"valuationDate":{"type":"string","format":"date","title":"Valuationdate","description":"Valuation date","default":"2026-10-28"},"dateTransport":{"anyOf":[{"type":"string","format":"date"},{"type":"null"}],"title":"Datetransport","description":"The date on which the legal ownership of a property is transferred from the seller to the buyer."}},"type":"object","required":["postalCode","houseNumber"],"title":"TransactionFinderInput"},"TransactionFinderResponse":{"properties":{"postalCode":{"type":"string","title":"Postalcode","description":"Postal code"},"houseNumber":{"type":"integer","title":"Housenumber","description":"House number"},"houseLetter":{"anyOf":[{"type":"string"},{"type":"null"}],"title":"Houseletter","description":"House letter"},"houseNumberExt":{"anyOf":[{"type":"string"},{"type":"null"}],"title":"Housenumberext","description":"House number extension"},"saleDate":{"anyOf":[{"type":"string","format":"date"},{"type":"null"}],"title":"Saledate","description":"Sale date"},"transportDate":{"anyOf":[{"type":"string","format":"date"},{"type":"null"}],"title":"Transportdate","description":"The date on which the legal ownership of a property is transferred from the seller to the buyer."},"transactionDate":{"anyOf":[{"type":"string","format":"date"},{"type":"null"}],"title":"Transactiondate","description":"The date on which the buyer and seller agreed on the property sale."},"transactionPrice":{"type":"integer","title":"Transactionprice","description":"Transaction price"},"transactionPriceIndexed":{"type":"integer","title":"Transactionpriceindexed","description":"The price of the transaction, indexed to the valuation date."},"transactionPriceIndexedDateTransport":{"anyOf":[{"type":"integer"},{"type":"null"}],"title":"Transactionpriceindexeddatetransport","description":"The price of the transaction, indexed to the transport date."},"transactionPriceIndexedDateSale":{"anyOf":[{"type":"integer"},{"type":"null"}],"title":"Transactionpriceindexeddatesale","description":"The price of the transaction, indexed to the sale date."},"valuationDate":{"type":"string","format":"date","title":"Valuationdate","description":"Valuation date"}},"type":"object","required":["postalCode","houseNumber","saleDate","transportDate","transactionPrice","transactionPriceIndexed","transactionPriceIndexedDateTransport","transactionPriceIndexedDateSale","valuationDate"],"title":"TransactionFinderResponse"},"ErrorObject":{"properties":{"code":{"type":"integer","title":"Code"},"message":{"type":"string","title":"Message"},"errors":{"items":{"$ref":"#/components/schemas/ErrorDetail"},"type":"array","title":"Errors"}},"type":"object","required":["code","message","errors"],"title":"ErrorObject"},"ErrorDetail":{"properties":{"reason":{"type":"string","title":"Reason"},"message":{"type":"string","title":"Message"}},"type":"object","required":["reason","message"],"title":"ErrorDetail"}}},"paths":{"/mx-transaction-finder":{"get":{"description":"Conveniently retrieve residential transaction data for a specific object.","operationId":"transactionFinder","parameters":[{"description":"Postal 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buyer.","required":false,"style":"form","explode":true,"schema":{"type":"string","format":"date"},"name":"dateTransport","in":"query"}],"responses":{"200":{"description":"TransactionFinderResponse","content":{"application/json":{"schema":{"properties":{"id":{"anyOf":[{"type":"string"},{"type":"null"}]},"params":{"$ref":"#/components/schemas/TransactionFinderInput"},"data":{"$ref":"#/components/schemas/TransactionFinderResponse"},"error":{"additionalProperties":{"type":"string"},"type":"object"},"meta":{"anyOf":[{"additionalProperties":{"type":"string"},"type":"object"},{"type":"null"}]},"status":{"type":"string"}},"type":"object","required":["data","status"]}}}},"400":{"description":"HTTP 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500","content":{"application/json":{"schema":{"properties":{"id":{"anyOf":[{"type":"string"},{"type":"null"}]},"params":{"$ref":"#/components/schemas/TransactionFinderInput"},"data":{"additionalProperties":{"type":"string"},"type":"object"},"error":{"$ref":"#/components/schemas/ErrorObject"},"meta":{"anyOf":[{"additionalProperties":{"type":"string"},"type":"object"},{"type":"null"}]},"status":{"type":"string"}},"type":"object","required":["error","status"]}}}}}}}}}
```

## The TransactionFinderResponse object

```json
{"openapi":"3.1.1","info":{"title":"Matrixian API","version":"1.0.0"},"components":{"schemas":{"TransactionFinderResponse":{"properties":{"postalCode":{"type":"string","title":"Postalcode","description":"Postal code"},"houseNumber":{"type":"integer","title":"Housenumber","description":"House number"},"houseLetter":{"anyOf":[{"type":"string"},{"type":"null"}],"title":"Houseletter","description":"House letter"},"houseNumberExt":{"anyOf":[{"type":"string"},{"type":"null"}],"title":"Housenumberext","description":"House number extension"},"saleDate":{"anyOf":[{"type":"string","format":"date"},{"type":"null"}],"title":"Saledate","description":"Sale date"},"transportDate":{"anyOf":[{"type":"string","format":"date"},{"type":"null"}],"title":"Transportdate","description":"The date on which the legal ownership of a property is transferred from the seller to the buyer."},"transactionDate":{"anyOf":[{"type":"string","format":"date"},{"type":"null"}],"title":"Transactiondate","description":"The date on which the buyer and seller agreed on the property sale."},"transactionPrice":{"type":"integer","title":"Transactionprice","description":"Transaction price"},"transactionPriceIndexed":{"type":"integer","title":"Transactionpriceindexed","description":"The price of the transaction, indexed to the valuation date."},"transactionPriceIndexedDateTransport":{"anyOf":[{"type":"integer"},{"type":"null"}],"title":"Transactionpriceindexeddatetransport","description":"The price of the transaction, indexed to the transport date."},"transactionPriceIndexedDateSale":{"anyOf":[{"type":"integer"},{"type":"null"}],"title":"Transactionpriceindexeddatesale","description":"The price of the transaction, indexed to the sale date."},"valuationDate":{"type":"string","format":"date","title":"Valuationdate","description":"Valuation date"}},"type":"object","required":["postalCode","houseNumber","saleDate","transportDate","transactionPrice","transactionPriceIndexed","transactionPriceIndexedDateTransport","transactionPriceIndexedDateSale","valuationDate"],"title":"TransactionFinderResponse"}}}}
```


---

# Agent Instructions
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```
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