I am trying to give you a perspective rather than a formal JD that would be more helpful. I hope my being technology head might help you.
A CTO would be the final authority to decide upon the Technology roadmap which will have a very strategic impact on the business at large (depending on the nature of the business of course). Understand that - the peers of CTO are the Sales, Finance and business development persons who are visualizing a business problems and constraints of the existing market (resources, finance, competitor's advantages etc.). So the CTO needs to start from there to transform into the targets of the various products, and infrastructures and deliver that within the acceptable time and most importantly for the available resources (human resource and capex) in the best way.
In the process CTO is responsible for all "technology decisions" as well as "development efforts" to produce the relevant work. Such decisions also include 'build vs. out source vs. buy', and which platform to work on and what new original work will be useful what might not make a business impact and hence not to over invest.
Now, don't view this as a one time affair. A good CTO knows, that time will change and new demands will come. Hence, under his capacity, she/he needs to keep up updating competence of ones' team and keep up better.
In a nut-shell, CTO is responsible for creating a team of competence
and suit of products (or service infrastructure) through continued
decisions and execution.
Trust me, it is really easier said than done!