xml tag name size

[karadoc]

The DLL has access to the following function in the xml interface:

// returns the tag name of the last located node, returns true if there is/was a last located node and false otherwise
virtual bool GetLastLocatedNodeTagName(FXml* xml, TCHAR* pszTagName) = 0;

I'd like to use this function, but I don't know how I can use it without risking a buffer overflow. Presumably the function will put the tag name inside pszTagName, but how do I know how big that buffer needs to be? Is there some maximum tag size that I can use? Or some other method for working out how big the tag is?