@techreport{TR-IC-PFG-26-10, number = {IC-PFG-26-10}, author = {Filipe Lacerda Benevides and Julio Cesar dos Reis}, title = {{Sponsored Discovery Mechanism for the Web of Open Agents}}, month = {July}, year = {2026}, institution = {Institute of Computing, University of Campinas}, note = {In English, 31 pages. \par\selectlanguage{english}\textbf{Abstract} As autonomous {LLM} agents become primary consumers of web services, they discover and delegate to one another in open ecosystems -- a \emph{Web of Open Agents} -- yet existing discovery infrastructures offer no principled way to govern how agents \emph{compete for visibility}, risking pay-to-win dynamics in which advertising spend, not merit, drives selection. We propose \emph{Sponsored Discovery}, whose core is {MACS} (Match-gated Agent Composite Score): semantic domain match acts as a \emph{multiplicative gate} that structurally bounds out-of-domain agents regardless of bid or reputation, coupled with a multi-dimensional behavioral reputation over accuracy, latency, and cost. Using real {LLM} agents that answer {MMLU-Pro} questions across three adversarial scenarios (honest baseline, domain-falsifying fraudster, {SLA}/cost-inflated agent), {MACS} achieves the highest delegation success across all three. Our results from a paired ablation show {MACS}'s advantage over a purely additive composite: \emph{decisive} under domain misreporting and \emph{marginal} in benign settings, where behavioral reputation alone suffices, while bid-only and quality-adjusted baselines are exploited. This study further analyzes its incentive properties and limits (calibrated misrepresentation, {Sybil} whitewashing). } }