Source

File: wp-includes/rest-api/endpoints/class-wp-rest-controller.php

public function get_endpoint_args_for_item_schema( $method = WP_REST_Server::CREATABLE ) {

		$schema                  = $this->get_item_schema();
		$schema_properties       = ! empty( $schema['properties'] ) ? $schema['properties'] : array();
		$endpoint_args           = array();
		$valid_schema_properties = array(
			'type',
			'format',
			'enum',
			'items',
			'properties',
			'additionalProperties',
			'minimum',
			'maximum',
			'exclusiveMinimum',
			'exclusiveMaximum',
			'minLength',
			'maxLength',
			'pattern',
			'minItems',
			'maxItems',
			'uniqueItems',
		);

		foreach ( $schema_properties as $field_id => $params ) {

			// Arguments specified as `readonly` are not allowed to be set.
			if ( ! empty( $params['readonly'] ) ) {
				continue;
			}

			$endpoint_args[ $field_id ] = array(
				'validate_callback' => 'rest_validate_request_arg',
				'sanitize_callback' => 'rest_sanitize_request_arg',
			);

			if ( isset( $params['description'] ) ) {
				$endpoint_args[ $field_id ]['description'] = $params['description'];
			}

			if ( WP_REST_Server::CREATABLE === $method && isset( $params['default'] ) ) {
				$endpoint_args[ $field_id ]['default'] = $params['default'];
			}

			if ( WP_REST_Server::CREATABLE === $method && ! empty( $params['required'] ) ) {
				$endpoint_args[ $field_id ]['required'] = true;
			}

			foreach ( $valid_schema_properties as $schema_prop ) {
				if ( isset( $params[ $schema_prop ] ) ) {
					$endpoint_args[ $field_id ][ $schema_prop ] = $params[ $schema_prop ];
				}
			}

			// Merge in any options provided by the schema property.
			if ( isset( $params['arg_options'] ) ) {

				// Only use required / default from arg_options on CREATABLE endpoints.
				if ( WP_REST_Server::CREATABLE !== $method ) {
					$params['arg_options'] = array_diff_key(
						$params['arg_options'],
						array(
							'required' => '',
							'default'  => '',
						)
					);
				}

				$endpoint_args[ $field_id ] = array_merge( $endpoint_args[ $field_id ], $params['arg_options'] );
			}
		}

		return $endpoint_args;
	}