Sir Cornflake's answer is spot-on. Your telepathic language would still need elements that distinguish meanings (as phonemes, cheremes, and graphemes do in speech, signing, and writing respectively). Your telepathic language would still need a lexicon and a grammar. Don't forget that, in addition to being able to express and understand language, using language internally is one of our thinking skills. So ... I don't see any reason for a telepathic language to confine itself to the use of tones.
As I see it, the chief advantage of a telepathic language would be the ability to integrate language with sensory data--visual, aural, tactile, somatic, gustatory, olfactory ... "images" from all the senses. The language could have a system of deixis that us non-telepaths would find unfamiliar--a system by which the telepaths could use their language to organize and integrate sensory data into their discourse. One could imagine it as a kind of 3-D to 4-D rebus. "Yesterday, I saw a [image of man located among memories of a certain time and place]." "[image of a buffalo located among memories of a certain time and place] struck me as majestic."
I don't know about the written form of the language. It would probably need many descriptors that would be obviated by the images embedded in most linguistic telepathic messages. But a civilization advanced enough to create practical radio-telepathy would also be advanced enough to create a way to record the language and the embedded images just as written Internet text can be full of hyperlinks.