Antaeus serves as a semantic policy engine designed for developers tasked with assessing human-written rules related to language, context, intent, or exceptions. It features an open-source core built in Go and a command-line interface that can load policy artifacts in YAML or JSON formats, validating these against versioned schemas while executing named regression tests. The evaluation process yields clear outcomes such as allow, review, deny, or failure, accompanied by policy identification and evidence for the decisions made, while leaving the responsibilities of authentication, authorization, and any consequential actions to the application itself. Developers have the option to operate a deterministic, credential-free local workflow or utilize an experimental hosted dashboard and API for managing policies and evaluating various inputs. Additionally, there is an experimental OpenAI evaluator available for use. It is important to note that Antaeus is still in its early stages; thus, the capacity of the hosted service is limited and does not come with a production-level service level agreement (SLA), which may affect reliability during high-demand situations.