Mergen vs observability tools for AI agents
This is not a “rip out Datadog” argument — keep your observability stack. It answers a different question. Datadog, Sentry, Grafana, and PagerDuty are post-incident tools: they detect, page, and help you diagnose after an action has executed. They have zero enforcement authority over an AI agent before its tool call runs.
Mergen is the inline gate — the category is Agent Execution Governance, not observability. When an agent calls terraform destroy prod, monitoring tells you it happened; Mergen returns a structured refusal in under a millisecond and the handler never executes. The two are complementary: Mergen even consumes PagerDuty webhooks and Datadog traces as incident context.
| Post-incident monitoring (Datadog + Sentry + PagerDuty) | Mergen (inline execution gateway) | |
|---|---|---|
| Execution control | None — agents run unrestricted; you learn what happened from dashboards and alerts. | Deterministic local gate blocks destructive tool calls in under 1ms, before the handler runs, and returns a guided alternative so the agent reformulates instead of stopping. |
| When it acts | After execution — alert fires once damage is observable. | Before execution — the hazardous call never reaches your runtime. |
| AI integration | Dashboards with AI summaries of what already happened. | MCP proxy in the call path: every tool call passes through policy before the handler runs. |
| Policy enforcement | System prompts and conventions — probabilistic, unenforced. | Override corpus: every human decision becomes binding, deterministic enforcement policy. |
| Human-in-the-loop | None — a human is paged after the fact. | Risky calls HOLD: the Promise is suspended and Slack approve/deny resumes or denies it before execution. |
| Audit trail | Logs of effects, reconstructed after the incident. | Hash-chained record of every intercepted action (the Agent Blunder Log) plus an append-only per-agent decision ledger. |
Use both — they answer different questions
Observability answers “what is my system doing?” An execution gateway answers “what is my agent allowed to do?” Teams granting autonomous write access to AI agents need an answer to the second question before the first one becomes an incident report.