Added some phpdocs for trade offers

TradeOffers.php

@@ -358,7 +358,7 @@ public function cancelTradeById($tradeOfferId)
 
     /**
      * Shortcut for creating a new trade offer with a user.
-     * @param mixed $accountId Account ID of the user you want to create a trade with.
+     * @param string $accountId Account ID of the user you want to create a trade with.
      * @return Trade
      */
     public function createTrade($accountId)

TradeOffers/Trade.php

@@ -43,6 +43,13 @@ public function jsonSerialize()
         ];
     }
 
+    /**
+     * @param int $appId
+     * @param int $contextId
+     * @param string $assetId
+     * @param int $amount
+     * @return bool
+     */
     public function addMyItem($appId, $contextId, $assetId, $amount = 1)
     {
         $asset = new TradeAsset($appId, $contextId, $assetId, $amount);
@@ -54,6 +61,13 @@ public function addMyItemByAsset(TradeAsset $asset)
         return $this->me->addItem($asset);
     }
 
+    /**
+     * @param int $appId
+     * @param int $contextId
+     * @param string $assetId
+     * @param int $amount
+     * @return bool
+     */
     public function addOtherItem($appId, $contextId, $assetId, $amount = 1)
     {
         $asset = new TradeAsset($appId, $contextId, $assetId, $amount);
@@ -133,7 +147,7 @@ public function getMessage()
     }
 
     /**
-     * @param string $message
+     * @param string $message Max length is 128 characters
      */
     public function setMessage($message)
     {