need another set of braces for composer.json?

the composer.json file would not work for me until I added an external set of braces around the supplied piece of code:

{"repositories": [
{
"type": "vcs",
"url": "http://github.com/engineyard/ey-php-performance-tools"
}
],
"require": {
"php": ">=5.3.3",
"engineyard/php-performance-tools": "dev-master"
}
}