# Technical specification

This technical specification explains the content of the OS Features API and the methods you can use to call it.

The OS Features API lets users call and interact with OS data, including the highly detailed OS MasterMap Topography Layer. It does this by exposing the data through an Open Geospatial Consortium Web Feature Service (OGC WFS).

{% hint style="info" %}
If you are not familiar with the OS Features API, please read the [overview documentation ](https://docs.os.uk/os-apis/accessing-os-apis/os-features-api)before proceeding.
{% endhint %}

## Core concepts

This specification does not cover core concepts that apply to all Ordnance Survey APIs.

Please read the following pages to learn more about OS API core concepts:

* [authentication](https://docs.os.uk/os-apis/core-concepts/authentication "mention")
* [error-codes](https://docs.os.uk/os-apis/core-concepts/error-codes "mention")
* [rate-limiting-policy](https://docs.os.uk/os-apis/core-concepts/rate-limiting-policy "mention")

## API reference

The OS Features API exposes data through an Open Geospatial Consortium Web Feature Service (OGC WFS).

The OGC WFS accepts three types of requests:

<table data-view="cards"><thead><tr><th></th><th></th><th data-hidden data-card-target data-type="content-ref"></th></tr></thead><tbody><tr><td><strong>getCapabilities</strong></td><td>Returns a metadata describing the WFS service .</td><td><a href="technical-specification/getcapabilities">getcapabilities</a></td></tr><tr><td><strong>describeFeatureType</strong></td><td>Returns a description of the attributes for each feature type.</td><td><a href="technical-specification/describefeaturetype">describefeaturetype</a></td></tr><tr><td><strong>getFeature</strong></td><td>Returns a selection of a specific features including its attribute values and geometry.</td><td><a href="technical-specification/getfeature">getfeature</a></td></tr></tbody></table>