I've tried GetRecords from ILS-DI and noticed that the id_type parameter listed doesn't work, although it's listed in documentation. <GetRecords><code>IllegalParameter</code><message>The parameter id_type is illegal.</message></GetRecords>
Works for me: /cgi-bin/koha/ilsdi.pl?service=LookupPatron&id=42&id_type=cardnumber returns <LookupPatron><id>51</id></LookupPatron>
And /cgi-bin/koha/ilsdi.pl?service=GetAvailability&id=1+2+99999&id_type=item returns <dlf:collection xsi:schemaLocation="http://diglib.org/ilsdi/1.1 http://diglib.org/architectures/ilsdi/schemas/1.1/dlfexpanded.xsd"><dlf:record><dlf:bibliographic id="1"/><dlf:items><dlf:item id="1"><dlf:simpleavailability><dlf:identifier>1</dlf:identifier><dlf:availabilitystatus>available</dlf:availabilitystatus><dlf:location>Centerville</dlf:location></dlf:simpleavailability></dlf:item></dlf:items></dlf:record><dlf:record><dlf:bibliographic id="345"/><dlf:items><dlf:item id="2"><dlf:simpleavailability><dlf:identifier>2</dlf:identifier><dlf:availabilitystatus>available</dlf:availabilitystatus><dlf:location>Centerville</dlf:location></dlf:simpleavailability></dlf:item></dlf:items></dlf:record><dlf:record><dlf:bibliographic id="99999"/><dlf:items><dlf:item id="99999"><dlf:simpleavailability><dlf:identifier>99999</dlf:identifier><dlf:availabilitystatus>unknown</dlf:availabilitystatus><dlf:availabilitymsg>Error: could not retrieve availability for this ID</dlf:availabilitymsg></dlf:simpleavailability></dlf:item></dlf:items></dlf:record></dlf:collection>
Scratch the last 2 comments, it was not GetRecords. It is in the POD since the first commit but has never been implemented. So either we implement it, or we remove it from POD and doc :)
I'd vote for removing it from the documentation as a first simple step.