MCP server hardening: redundancy, rate limits, abuse and threat review

Audit the public MCP surface against the latest model-context-protocol best practices. Revisit per-key and per-IP rate limits, add a circuit breaker for sustained abuse, instrument health and response-time SLOs with auto-failover to a warm replica, redact secrets from error responses, threat-model the tool surface (prompt injection via tool descriptions, scope escalation), and document the security posture publicly. Roll the resulting controls into the existing API rate limiting and abuse hardening card rather than duplicating that work.