parameter description is not showed up when it contains other parameters names

example below:

``` apib
## add coupon to single user [GET /couponagent/addCoupon{?userid,discount_money,limit_money}]
+ Parameters
* userid: `101649899` (number,required) - userid
* discount_money: `1.01` (number,required) - money amout to be discounted
* limit_money: `-1` (number,required) - -1 represents (discount_money+1) could be used
```

argument `limit_money` description includes argument name `discount_money`, which leads its description was not showed up