What tools or methods have you used to describe and document APIs?

Tools commonly used for describing and documenting APIs in PHP include:

• Swagger / OpenAPI — allows describing REST APIs in YAML or JSON format, which can then be used to generate interactive documentation.
• ApiDoc — a tool for generating documentation from comments in the code.
• PHPDoc — a standard for documenting code, including descriptions of methods and parameters, which helps in generating documentation.

Example of using PHPDoc for an API method:

/**
 * Get a list of users.
 *
 * @return array Array of users
 */
public function getUsers(): array {
    // ...
}

You can also use integration with Postman for testing and documenting APIs.