intermediary between an agent (freelancer) and the principals who hire him. The platform has

control over pricing structures and usually treats social welfare as a ﬁrst-order concern [27, p. 55].

Other examples include marketing agencies (multiple advertisers and a single marketing agent),

corporate management (multiple managers and shareholders, and a single lower-level manager),

etc.

Our goal in this work is to import ideas from VCG contracts and auctions to the incomplete

information world, towards making progress on the long-standing problem of welfare maximization

in common agency settings. Our ﬁrst challenge is that the class of VCG contracts is undeﬁned

for incomplete information settings. After devising an appropriate generalization of the deﬁnition

(Section 3.4), we uncover a more serious challenge – the adaptation of VCG contracts to incomplete

information introduces negative payments.

In other words, under such contracts the agent is
Incomplete Information VCG Contracts for Common Agency