NSService

gistfile1.xml

<key>NSServices</key>
    <array>
        <dict>
            <key>NSMenuItem</key>
            <dict>
                <key>default</key>
                <string>Tweet</string>
            </dict>
            <key>NSMessage</key>
            <string>tweetService</string>
            <key>NSPortName</key>
            <string>Twitter</string>
            <key>NSRequiredContext</key>
            <dict>
                <key>NSServiceCategory</key>
                <string>public.item</string>
            </dict>
            <key>NSSendTypes</key>
            <array>
                <string>NSStringPboardType</string>
            </array>
        </dict>
    </array>