Facebook: show open graph dialog when posting expects object reference

I want to show the open graph dialog to allow users to write a message before post on their timeline. I'm trying to use the share_open_graph dialog but for some reason it says that the action is not referencing the object.

I know that there are some questions about it, but it didn't help me. Also, I would like to know why my second code works (I know that not shows the dialog) and why the first one no, and when I find the solution, why this solution.

This is my code using the Facebook open graph dialog:

FB.ui({
    method: 'share_open_graph',
    action_type: 'alexdecasa:decorate',
    action_properties: JSON.stringify({
        room: {
            "url": image,
            "title": "Supply title",
            "description": "Supply description",
            "image": image
        }
    })
}, function(response){});

My action is decorate and the object is room. As you can see I'm referencing the object inside the action_properties.

Using FB.api code works:

FB.api(
    'me/alexdecasa:decorate',
    'post',
    {
        room: {
            "url": image,
            "title": "Supply title",
            "description": "Supply description",
            "image": image
        }
    },
    function(response) {});