> For the complete documentation index, see [llms.txt](https://docs.altum.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.altum.ai/english/property-valuation-and-market/market-trend-api/authentication-input-and-response.md).

# Authentication, input and response

### Headers

<table><thead><tr><th width="152">Name</th><th width="145">Type</th><th>Description</th></tr></thead><tbody><tr><td>Content-Type</td><td>string</td><td>application/json</td></tr><tr><td>x-api-key<mark style="color:red;">*</mark></td><td>string</td><td>Unique API key from Altum. Obtain one via Mopsus (https://mopsus.altum.ai)</td></tr></tbody></table>

This is the main endpoint of the API. It retrieves a list of subsidies based on a user's postcode and, if provided, their personal and financial details for loan eligibility checking.

<mark style="color:green;">**`GET`**</mark>   `https://api.altum.ai/market-trend?postcode=??&valuation_date=????-??-??`

### Request body

**Market Trend Request Model**

| **Field**                                  | **Type** | **Description**                                     |
| ------------------------------------------ | -------- | --------------------------------------------------- |
| postcode<mark style="color:red;">\*</mark> | string   | **Required**. The Dutch postcode (e.g., "3511 AA"). |
| valuation\_date                            | date     | Reference date for price indexing (YYYY-MM-DD).     |

**Example Complete Input**

```
https://api.altum.ai/market-trend?postcode=5258BB&valuation_date=2024-01-15
```

Upon a successful `GET` request, the API returns a `200 OK` status with a JSON object containing the results.

### Market Trend API Response Model

| **Field**                       | **Type** | **Description**                                                                                                                 |
| ------------------------------- | -------- | ------------------------------------------------------------------------------------------------------------------------------- |
| postcode                        | String   | The normalized Dutch postcode (e.g., "1011AB") used for the query.                                                              |
| city                            | String   | The city name derived from the master address database.                                                                         |
| neighbourhood                   | String   | The specific neighborhood name (if available in Dataland source).                                                               |
| municipality                    | String   | The administrative municipality governing the area.                                                                             |
| averagePriceSingleFamilyHomes   | Float    | The average transaction price for single-family properties (detached, semi-detached, terraced).                                 |
| averagePriceMultiFamilyHomes    | Float    | The average transaction price for multi-family properties (apartments/flats).                                                   |
| pricePerSquareMeterSingleFamily | Float    | The average price per square meter (€/m²) for single-family homes.                                                              |
| pricePerSquareMeterMultiFamily  | Float    | The average price per square meter (€/m²) for apartments.                                                                       |
| annualPriceChange               | Float    | The annualized percentage growth (CAGR) of property values compared to the previous recorded year.                              |
| fiveYearPriceChange             | Float    | The projected percentage change in value over a 5-year period based on historical growth trends.                                |
| totalSalesLast12Months          | Integer  | The total count of property transactions recorded in this postcode over the last 365 days.                                      |
| priceDistribution               | Object   | A dictionary serving as a histogram, mapping price ranges (e.g., "250-500k") to the number of properties sold in that bracket.  |
| pricePerSquareMeterDistribution | Object   | A dictionary serving as a histogram, mapping price-per-m² ranges (e.g., "3000-3500") to the frequency of sales in that bracket. |

### Output <a href="#id-5.-output" id="id-5.-output"></a>

Upon a successful `GET` request, the API returns a `200 OK` status with a JSON object containing the results.

**Example Complete Output**

```
{
  "valuationDate": "2024-01-15",
  "region": {
    "postcode": "5258BB",
    "city": "BERLICUM NB",
    "neighbourhood": "Berlicum",
    "municipality": "Sint-Michielsgestel"
  },
  "averagePriceSingleFamilyHomes": 585213.2,
  "averagePriceMultiFamilyHomes": null,
  "pricePerSquareMeterSingleFamily": 3862.19,
  "pricePerSquareMeterMultiFamily": null,
  "annualPriceChange": 2.34,
  "fiveYearPriceChange": 12.25,
  "transactionData": {
    "totalSalesLast12Months": 0
  },
  "priceDistribution": {
    "250-500k": 3,
    "500-750k": 1,
    "750k-1M": 1
  },
  "pricePerSquareMeterDistribution": {
    "0-2500": 1,
    "2500-3000": 1,
    "4000+": 3
  }
}
```

**Explanation**

🏘️ **Valuation Date**

```
"valuationDate": "2024-01-15"
```

{% hint style="info" %}
All data and KPIs are calculated using the prices as of the valuation date and reflect the price levels prevailing on that date.
{% endhint %}

🏘️ **Region**

```
"region": {
  "postcode": "5258BB",
  "city": "BERLICUM NB",
  "neighbourhood": "Berlicum",
  "municipality": "Sint-Michielsgestel"
}
```

{% hint style="info" %}
All the data and KPIs are calculated for postcode 5258BB, providing context at the city **BERLICUM NB**, neighborhood **Berlicum**, and municipality **Sint-Michielsgestel**.
{% endhint %}

💰 **Average Property Prices**

```
"averagePriceSingleFamilyHomes": 585213.2,
"averagePriceMultiFamilyHomes": null
```

{% hint style="info" %}

* **Single-family homes:** €585213.2 on average.
* **Multi-family homes / apartments:** No data available for this area.

This tells us that houses in this postcode are relatively expensive, and the market for apartments is either very small or not recorded.
{% endhint %}

📏 **Price Per Square Meter**

```
"pricePerSquareMeterSingleFamily": 3862.19,
"pricePerSquareMeterMultiFamily": null
```

{% hint style="info" %}

* **Single-family homes:** €3862.19 per m².
* **Multi-family homes:** No data available.

This gives a way to compare house prices fairly, even if the sizes of the houses differ.
{% endhint %}

📈 **Price Trends**

```
"annualPriceChange":  2.34,
"fiveYearPriceChange": 12.25
```

{% hint style="info" %}

* **Annual price change:** +2.34% → prices increased over the last year.
* **Five-year price change:** +12.25% → prices increased significantly over the last 5 years.

This shows that house prices are rising in both the short term and long term.
{% endhint %}

🏷️ **Transaction Activity**

```
"transactionData": {
  "totalSalesLast12Months": 0
}
```

{% hint style="info" %}

* **Number of sales in the last 12 months:** 0

This means **no houses were sold in this area over the past year**, so the market is currently inactive.
{% endhint %}

💵 **Price Distribution**

```
 "priceDistribution": {
		"250-500k": 3,
		"500-750k": 1,
		"750k-1M": 1
	}
```

{% hint style="info" %}

* How many houses were sold in each price range (all-time, not just last 12 months):

  * €250k–€500k → 3 houses
  * €500k–€750k → 1 houses
  * €1M+ → 1 houses

  Most houses sold in this postcode fall in the **€500k–€750k range**, with a few high-end sales over €1M.
  {% endhint %}

🏠 **Price Per Square Meter Distribution**

```
"pricePerSquareMeterDistribution": {
		"0-2500": 1,
		"2500-3000": 1,
		"4000+": 3
	}
```

{% hint style="info" %}
This tells us that even expensive houses are relatively modest in €/m² compared to very high-end markets.

* €0–€2500 → 3 houses&#x20;
* €2500–€3000 → 1 houses
* €4000+ → 3 houses
  {% endhint %}

{% tabs %}
{% tab title="200: OK Standard response" %}

```
Request processed and data returned.
```

{% endtab %}

{% tab title="400: Bad Request Unsuccessful response" %}

```
The postcode exists, but there is insufficient data (e.g., missing dates or prices) to calculate KPIs.
```

{% endtab %}

{% tab title="404 Not Found" %}

```
No transactions or master data exist for the provided postcode.
```

{% endtab %}

{% tab title="422 Validation Error" %}
The postcode format was incorrect (e.g., "12345").
{% endtab %}

{% tab title="500: Internal Server Error Service is not available and/or down" %}

```
Database connection failure or unhandled exception in calculation logic.
```

{% endtab %}
{% endtabs %}


---

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