The type library definition looks as follows:
<tag>
<description>Call ITP Server</description>
<name>ServerCall</name>
<tag-class>…</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>name</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>type</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>value</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>parameters</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>