You really should document each:

• Attribute declaration.

• Embedded element declaration.

• Unique, Key, or Keyref Constraint.

An example:

<xs:schema xmlns:h="http://www.w3.org/1999/xhtml" ...>
...
<xs:element name="person" type="my:Person">
  <xs:annotation>
  <xs:documentation>
    <h:p>This element is use to describe a person's information such as name, email, address.</h:p> 
  </xs:documentation>
  </xs:annotation>
</xs:element>

<xs:complexType name="Person">
  <xs:sequence>
    <xs:element name="name" type="xs:string">
      <xs:annotation>
        <xs:documentation>
        <h:p>This element contains the name of the person.</h:p>
        </xs:documentation>
      </xs:annotation>
    </xs:element>
    <xs:element name="name" type="xs:string" minOccurs="0">
      <xs:annotation>
        <xs:documentation>
        <h:p>This element contains the person's email address in full domain format (e.g. you@yourdomain.com).</h:p>
        </xs:documentation>
      </xs:annotation>
    </xs:element>
  </xs:sequence>
  <xs:attribute name="id" type="xs:ID">
     <xs:annotation>
       <xs:documentation>
       <h:p>This attribute is used to provide a identifier for cross referencing within the document.</h:p>
       </xs:documentation>
     </xs:annotation>
  </xs:attribute>
</xs:complexType>

</xs:schema>