  We study the problem of designing mechanisms for \emph{information
acquisition} scenarios. This setting models strategic interactions between an
uniformed \emph{receiver} and a set of informed \emph{senders}. In our model
the senders receive information about the underlying state of nature and
communicate their observation (either truthfully or not) to the receiver,
which, based on this information, selects an action. Our goal is to design
mechanisms maximizing the receiver's utility while incentivizing the senders to
report truthfully their information. First, we provide an algorithm that
efficiently computes an optimal \emph{incentive compatible} (IC) mechanism.
Then, we focus on the \emph{online} problem in which the receiver sequentially
interacts in an unknown game, with the objective of minimizing the
\emph{cumulative regret} w.r.t. the optimal IC mechanism, and the
\emph{cumulative violation} of the incentive compatibility constraints. We
investigate two different online scenarios, \emph{i.e.,} the \emph{full} and
\emph{bandit feedback} settings. For the full feedback problem, we propose an
algorithm that guarantees $\tilde{\mathcal O}(\sqrt T)$ regret and violation,
while for the bandit feedback setting we present an algorithm that attains
$\tilde{\mathcal O}(T^{\alpha})$ regret and $\tilde{\mathcal
O}(T^{1-\alpha/2})$ violation for any $\alpha\in[1/2, 1]$. Finally, we
complement our results providing a tight lower bound.
