Auth0 vs Clerk vs Firebase Auth for AI Agents — AN Score Comparison

Auth0 vs Clerk vs Firebase Auth for AI Agents — AN Score Comparison When your agent needs to authenticate API calls, three platforms dominate: Clerk (execution-first), Auth0 (enterprise compliance), and Firebase Auth (Google ecosystem). This comparison uses Rhumb AN Scores — a 20-dimension framework specifically designed for evaluating APIs agent-readiness. We measure execution reliability, access patterns, governance requirements, and real failure modes. The Scores Provider AN Score Execution Access Readiness Governance Confidence Clerk 7.4 8.3 7.1 8.0 82% Auth0 6.3 6.8 5.0 9.0 71% Firebase Auth 6.3 7.5 4.8 7.0 68% Clerk: "Default for agent builders" (7.4 / 10) Best for: Agents that need the cleanest path from API key to user management. Modern API design, highest execution score, most agent-friendly SDK. Biggest friction: JWT clock skew causes intermittent auth rejections in distributed systems. Webhook delivery has no retry — lost events stay lost. Both require defensive coding from