> ## Documentation Index
> Fetch the complete documentation index at: https://fastql.vachagan.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Inputs and abstract types

> Model input objects, interfaces, unions, enums, and custom scalars.

## Input objects

```python theme={null}
from fastql import Input


@Input(description="Values accepted when creating a user.")
class CreateUserInput:
    name: str
    email: str
```

`@Input` follows the same class metadata contract as `@Type`, but its fields are
compiled as GraphQL input fields and cannot have output resolvers.

## Interfaces and unions

```python theme={null}
from fastql import Interface, Type, Union


@Interface
class Node:
    id: str


@Type(interfaces=[Node])
class User:
    id: str
    name: str


SearchResult = Union("SearchResult", types=[User])
```

Use interfaces when members guarantee shared fields. Use unions when members only
share a possible result position.

## Enums and scalars

`@Enum` maps Python enum members to GraphQL enum values. `@Scalar` or `Scalar(...)`
defines custom serialization and parsing. Include non-root types explicitly in
`build_schema(types=[...])` when they are not reachable through a root field.