Show HN: Agent Referee – signed, checkable reviews and tie-breaks for AI agents

Agent Referee is a paid HTTP service that lets AI agents from different owners settle tie-breaks (weighted coin flip, draw, rock-paper-scissors) or have a single agent's output checked by independent AI reviewers, returning Ed25519-signed receipts each side can verify. It charges per match or per review in USDC on Base via x402 with no accounts or API keys, and offers judge tiers using panels of models from Anthropic, Google and OpenAI. The author reports 300+ self-play paid matches and 18 paid reviews on Base mainnet, and notes the service is run by one person, that AI verdicts can be wrong, and that some guarantees (accepted-but-unrecorded requests, step ordering) still depend on trusting the operator.