Open Graph object callback gets truncated. Is there a character limit?

Question

I'm publishing actions to the user's timeline by posting to graph.facebook.com as described in the tutorial in Facebook's documentation.

 FB.api(
        '/me/[YOUR_APP_NAMESPACE]:cook?recipe=http://fbwerks.com:8000/zhen/cookie.html',
        'post',
        function(response) {
           if (!response || response.error) {
              alert('Error occured');
           } else {
              alert('Cook was successful! Action ID: ' + response.id);
           }
        });

However, when Facebook calls my object URL, I'm not receiving all the GET params that I passed through and it looks like Facebook is truncating the URL. Is there a character limit on the size of the object URL? The URL works fine when I put it in the object debugger.