How Specific Does Card Naming Have to Be
You have to be able to uniquely identify the card, you don't necessarily have to get the name correct.

The reason for this is while the Comprehensive Rules say you have to actually name the card (CR 201.3), the Tournament Rules state that you can get the Oracle text of the card (which includes the name) as long as you can uniquely identify it (MTR 3.6). In order to not waste time calling a judge to get the Oracle text of a card every time you need to name a card you just need to uniquely identify a card in order to 'name' it.

For example in a standard tournament if I wanted to name Jace, the Living Guildpact I couldn't just say "Jace" since Jace, Vryn&#39;s Prodigy is also in Standard, and that doesn't uniquely identify which one you are talking about. However you could say "The Jace that doesn't transform" or "The Jace that costs 4" since both of those statements uniquily identifies what card you are talking about in Standard. Note that in Modern you would need to find a different way to describe the card since both of those statements also describe Jace, Architect of Thought

Note that for transforming or flip cards for the Conundrum Sphinx, or something like Memoricide it doesn't matter what name you pick (or uniquely identify), but it does matter for cards like Pithing Needle. For those you have to identify the appropriate side, so if you wanted to name Jace, Telepath Unbound for Pithing Needle you could say "The transformed version of Jace" or something similar.