I need a recommendation for monitoring latency, failures, and token cost in a production agent

For a production agent, I’d recommend OpenTelemetry for traces/metrics/logs, paired with a cost-aware LLM observability layer like Langfuse, Helicone, or Arize Phoenix depending on your stack.

Best practical setup

1) Core observability: OpenTelemetry

Use this to capture:

• Latency per request, step, tool call, and model call
• Failures with error context and stack traces
• Distributed traces across agent steps, retrieval, tools, and downstream services

Why:

• Vendor-neutral
• Works well in production
• Integrates with Datadog, Grafana/Tempo, Honeycomb, New Relic, etc.

2) LLM-specific monitoring: Langfuse or Helicone

Use one of these to capture:

• Token usage
• Prompt/completion costs
• Model-level latency
• Per-request traces
• Conversation/session replay
• Prompt/version tracking

Good choices:

• Langfuse: strong tracing + prompt management + open-source/self-hostable
• Helicone: easy proxy-based setup, very good for API usage analytics and cost tracking
• Arize Phoenix: great for evaluation and tracing, especially if you want deeper LLM debugging

What I’d pick

• If you want open-source + self-hostable: Langfuse + OpenTelemetry
• If you want fastest time-to-value for API cost tracking: Helicone
• If you want strong evaluation/debugging workflows: Phoenix
• If you already use an APM: OpenTelemetry → Datadog/Grafana/Honeycomb, plus an LLM layer for token cost

Minimum metrics to track

• Request latency: p50/p95/p99
• Step latency: planner, retrieval, tool execution, generation
• Error rate: timeout, tool failure, model API failure, parsing failure
• Token usage: input, output, total
• Cost per request
• Retries
• Tool call counts
• Context size / prompt size
• User/session success rate

Recommended architecture

• Instrument your agent with OpenTelemetry spans
• Record each LLM call as a span with:
  • model name
  • prompt/completion token counts
  • estimated cost
  • error status
• Export traces to:
  • Langfuse/Helicone for LLM analysis
  • Datadog/Grafana/Honeycomb for infra + latency dashboards

If you want a simple default recommendation

Use OpenTelemetry + Langfuse.
That’s the most balanced choice for production: good visibility into latency/failures, plus token/cost tracking.

If you want, I can also give you:

1. a vendor comparison table, or
2. a reference architecture for instrumenting an agent in Python/Node.