As a native German I've never heard this adjective used to describe a person, only hugs or welcomes ("Herzlich wilkommen!", "Eine herzliche Umarmung."). If you wanted to describe someone as kind or nice you would use "lieb" or "nett" for the most part. The sentence as is sounds very strange.
Don't worry as a native English speaker I would never say "I am cordial" either. Perhaps the translation is valid...something one would never say.
Whether or not you meant it as a compliment, I'm tickled pink by your response :)
Herzlichen Dank, Gosha.
Out of interest - Context Reverso comes up with ONE occurrence - ich bin zu herzlich - Juliet says it to Romeo. She says - I would have played hard-to-get, but 'in truth, fair Montague, I am too fond'.
So it does have a use. If you happen to be translating Shakespeare. :)
In English we say warmhearted. http://www.merriam-webster.com/dictionary/warmhearted
Hearty in English is usually used in reference to a big, heavy and filling meal. "A hearty meal" would be like a big bowl of stew, a shepherd pie or something like that (good warming winter foods). "A hearty lunch" could be like a ploughman's lunch, strong thickly cut Cheddar cheese, a shallot onion and thick doorstep bread.
"Herzlich" to me means "heartfelt" eg: "Herzlich wilkommen!" = warm/heartfelt welcome, "Herzliche Danke" = heartfelt thanks.
In the sentence provided, it to me says "I am heartfelt" or "I am sincere".
I googled the answer and it told me that herzlich meant cordial, cordially , hearty. http://www.wordhippo.com/what-is/the-meaning-of/german-word-herzlich.html