  We consider a dynamic moral hazard problem between a principal and an agent,
where the sole instrument the principal has to incentivize the agent is the
disclosure of information. The principal aims at maximizing the (discounted)
number of times the agent chooses a particular action, e.g., to work hard. We
show that there exists an optimal contract, where the principal stops
disclosing information as soon as its most preferred action is a static best
reply for the agent or else continues disclosing information until the agent
perfectly learns the principal's private information. If the agent perfectly
learns the state, he learns it in finite time with probability one; the more
patient the agent, the later he learns it.
