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

# Overview

> Apivalk is built on the philosophy of **Documentation-Driven Development**. This means that your API's documentation is not an afterthought, but the core engine that drives the framework.

## Core Principle: Single Source of Truth (SSOT)

In Apivalk, your PHP code is the single source of truth. By defining the structure and validation rules of your requests and responses once, you gain:

1. **Automated Validation**: Requests are validated against the documentation before reaching your controller.
2. **Type Safety**: Input data is automatically cast to the correct PHP types.
3. **IDE Support**: DocBlocks are generated to provide autocompletion for request parameters.
4. **OpenAPI Specification**: A full OpenAPI 3.0 (Swagger) JSON is generated automatically.
5. **Reusable Components**: Standard response objects can be reused across multiple endpoints.

## The Documentation Flow

1. **Define**: You implement `getRequestDocumentation()` and `getResponseDocumentation()` in your controllers using the **Property System**.
2. **Generate DocBlocks**: Use the `DocBlockGenerator` to create "Shape" classes and update your request classes with `@property` tags.
3. **Run & Validate**: The `RequestValidationMiddleware` uses your definitions to validate incoming data.
4. **Export**: The `OpenAPIGenerator` crawls your routes and documentation to produce a Swagger file.

## Key Subsystems

* [**Request Documentation**](/documentation/request): Defining endpoint input contracts.
* [**Response Documentation**](/documentation/response): Defining endpoint output contracts.
* [**Property Collections**](/documentation/property-collection): Property Collections in Apivalk are used to group multiple properties together.
* [**Property System**](/documentation/property): The building blocks for defining data types and validation rules.
* [**DocBlock Generator**](/documentation/docblock-generator): Enhances the developer experience with IDE support.
* [**OpenAPI Generator**](/documentation/openapi-generator): Converts your code-based documentation into a standard format, including automatic security scheme discovery.
* [**Response Objects**](/documentation/response-objects): Pre-defined reusable objects for common API responses.