# Extending JSON-LD AND Hydra Contexts
## JSON-LD
Watch the JSON-LD screencast
API Platform Core provides the possibility to extend the JSON-LD context of properties. This allows you to describe JSON-LD-typed
values, inverse properties using the `@reverse` keyword and you can even overwrite the `@id` property this way. Everything you define
within the following annotation will be passed to the context. This provides a generic way to extend the context.
```php
[
"@id" => "http://yourcustomid.com",
"@type" => "http://www.w3.org/2001/XMLSchema#string",
"someProperty" => [
"a" => "textA",
"b" => "textB"
]
]
]
)]
public $name;
// ...
}
```
The generated context will now have your custom attributes set:
`GET /contexts/Book`
```json
{
"@context": {
"@vocab": "http://example.com/apidoc#",
"hydra": "http://www.w3.org/ns/hydra/core#",
"name": {
"@id": "http://yourcustomid.com",
"@type": "http://www.w3.org/2001/XMLSchema#string",
"someProperty": {
"a": "textA",
"b": "textB"
}
}
}
}
```
Note that you do not have to provide the `@id` attribute. If you do not provide an `@id` attribute, the value from `iri` will be used.
## Hydra
Watch the Hydra screencast
It's also possible to replace the Hydra context used by the documentation generator:
```php
["hydra_context" => ["foo" => "bar"]]
])]
class Book
{
//...
}
```
```yaml
# api/config/api_platform/resources.yaml
App\Entity\Book:
itemOperations:
get:
hydra_context: { foo: 'bar' }
```
```xml
bar
```