Trello

var key = "KEY";
var token = "TOKEN";
var board_id = "BOARD ID";
var card_no = 1;

var Trello = require("node-trello");
var t = new Trello(key, token);

t.post('/1/boards/' + board_id + '/cards/' + card_no + '/actions/comments', {
    text: "Comment text"
}, function(err, data){
    if (err) {
        console.log("err " + err);
    } else {
        console.log(data);
    }
});