Cedar Beats OPA for MCP Access Control on Safety-Critical Properties

A head-to-head benchmark of OPA/Rego against AWS Cedar for MCP tool access shows Cedar wins where it matters most: mathematically verifiable policies (Cedar Analysis can formally prove correctness), zero runtime exceptions (Rego failed multiple tests), and full static analyzability. For agent contexts where a policy bug allows unintended tool execution, Cedar's constraint model is the safer choice. OPA retains edge for complex operational logic.