# Schemas

Standardized Pydantic response models for consistent API responses across your FastAPI application.

## Overview

The `schemas` module provides generic response wrappers that enforce a uniform response structure. All models use `from_attributes=True` for ORM compatibility and `validate_assignment=True` for runtime type safety.

## Response models

### [`Response[T]`](../reference/schemas.md#fastapi_toolsets.schemas.Response)

The most common wrapper for a single resource response.

```python
from fastapi_toolsets.schemas import Response

@router.get("/users/{id}")
async def get_user(user: User = UserDep) -> Response[UserSchema]:
    return Response(data=user, message="User retrieved")
```

### [`PaginatedResponse[T]`](../reference/schemas.md#fastapi_toolsets.schemas.PaginatedResponse)

Wraps a list of items with pagination metadata and optional facet values. The `pagination` field accepts either [`OffsetPagination`](../reference/schemas.md#fastapi_toolsets.schemas.OffsetPagination) or [`CursorPagination`](../reference/schemas.md#fastapi_toolsets.schemas.CursorPagination) depending on the strategy used.

#### [`OffsetPagination`](../reference/schemas.md#fastapi_toolsets.schemas.OffsetPagination)

Page-number based. Requires `total_count` so clients can compute the total number of pages.

```python
from fastapi_toolsets.schemas import PaginatedResponse, OffsetPagination

@router.get("/users")
async def list_users() -> PaginatedResponse[UserSchema]:
    return PaginatedResponse(
        data=users,
        pagination=OffsetPagination(
            total_count=100,
            items_per_page=10,
            page=1,
            has_more=True,
        ),
    )
```

#### [`CursorPagination`](../reference/schemas.md#fastapi_toolsets.schemas.CursorPagination)

Cursor based. Efficient for large or frequently updated datasets where offset pagination is impractical. Provides opaque `next_cursor` / `prev_cursor` tokens; no total count is exposed.

```python
from fastapi_toolsets.schemas import PaginatedResponse, CursorPagination

@router.get("/events")
async def list_events() -> PaginatedResponse[EventSchema]:
    return PaginatedResponse(
        data=events,
        pagination=CursorPagination(
            next_cursor="eyJpZCI6IDQyfQ==",
            prev_cursor=None,
            items_per_page=20,
            has_more=True,
        ),
    )
```

The optional `filter_attributes` field is populated when `facet_fields` are configured on the CRUD class (see [Filter attributes](crud.md#filter-attributes-facets)). It is `None` by default and can be hidden from API responses with `response_model_exclude_none=True`.

### [`ErrorResponse`](../reference/schemas.md#fastapi_toolsets.schemas.ErrorResponse)

Returned automatically by the exceptions handler.

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[:material-api: API Reference](../reference/schemas.md)