What standard applies to ID-card? ISO-7816 T=0 or T=1 protocol?
ID-card supports both T=0 and T=1 protocols, default selection should be T=0. Here you can find some of the standards and technical documents related to the ID-card that are above all meant for software developers.
If the question is about compatible card readers then it should be enough if the reader is asynchronous and supports T=0 and T=1 protocols. In practice though it should definitely be tested if specific card reader works with the Estonian ID-card.