# Properties

Properties are user defined key-value pairs used to label resources such as {class}`tket:pytket.circuit.Circuit`, {ref}`jobs<jobs>` and {class}`tket:pytket.backends.backendresult.BackendResult`. This enables users to search through their resources using this custom defined metadata. There are four property value types:

```{eval-rst}
.. list-table::
   :widths: 100 100
   :header-rows: 1

   * - Property Type
     - Description
   * - String
     - Text value such as "Carbon"
   * - Boolean
     - True or False
   * - Float
     - Floating point number i.e. 0.237
   * - Int
     - Integer value i.e. 56, 1024

```

Most nexus API endpoints offer the ability to filter resources by property value.

:::{note}
Properties are currently scoped to {ref}`projects<projects>` and must be created before they are used. They can be created in the Nexus UI under the 'resource properties' tab within a project.
:::

## Auto Labelling

If a job creates a resource, Nexus will set the same property from the job onto the resource it creates. For example, if an execute job was created with the property {code}`parameter1: 0.5`, the result would also have it.

```{image} ./images/property_inheritance.png
:width: 500
```

## Required Properties

Properties can be made non-optional (required) which ensures all project collaborators label their resources. If a user fails to set a value for a required property, the API will return with an error.