Custom Fields in FetchXML

I'm using the fetchxml tester from XrmToobox. I've not able to see my custom fields in the output, but i can see system fields. For the xml given below, i can see activityId from appointment entity, but can see my customfield1 - any help on how to do this for a view? 

<fetch version="1.0" output-format="xml-platform" mapping="logical" distinct="false" >
<entity name="activitypointer" >
<attribute name="subject" />
<attribute name="activitytypecode" />
<attribute name="regardingobjectid" />
<attribute name="statecode" />
<attribute name="scheduledstart" />
<attribute name="ownerid" />
<attribute name="scheduledend" />
<attribute name="modifiedon" />
<order attribute="subject" descending="false" />
<filter type="and" >
     <condition attribute="scheduledstart" operator="on-or-after" value="2015-01-01" />
         <filter type="or" >
            <condition attribute="activitytypecode" operator="eq" value="4201" />
             <condition attribute="activitytypecode" operator="eq" value="4210" />
         </filter>
</filter>
<attribute name="activityid" />
<link-entity link-type="outer" name="appointment" from="activityid" to="activityid" >
    <attribute name="activityid" />
     <attribute name="custom1" />
</link-entity>
</entity>
</fetch>