Chapter 19 — Observability¶

Example: 35_observability_demo.mty.

Production agent development is mostly "why is this slow / expensive". Mighty owns that workflow with std.observe: auto-record every LLM call under MTY_OBSERVE=1, read it back with mty inspect --cost.

Shipped in v0.30 Track D.

Two-line trial¶

# 1. Run anything that hits an LLM under the observe env flag.
MTY_OBSERVE=1 mty run examples/28_agent_with_llm_field.mty

# 2. Read it back — total $$, per-provider breakdown, p50/p95/p99.
mty inspect --cost

Sample output:

LLM cost summary (last 24h)
  total: $0.18  calls: 12
  by provider:
    anthropic:  $0.14   8 calls  p50= 1.8s  p95= 4.2s  p99= 5.1s
    openai:     $0.04   4 calls  p50= 1.1s  p95= 2.3s  p99= 2.4s

Environment variables¶

Variable	Default	Effect
`MTY_OBSERVE`	unset	When `=1` / `on` / `true`, every `complete()` records to the active store.
`MTY_OBSERVE_DB`	`~/.mty/observations.sqlite`	SQLite path the recorder writes to and `mty inspect --cost` reads from.
`MTY_OBSERVE_OTEL`	unset	When set to an OTLP/HTTP base URL, recording redirects to the OTel exporter.
`MTY_PRICING_OVERRIDE`	unset	Path to a TOML pricing override (your contracted rate, not the public rate card).

What gets recorded¶

Per LLM call, the recorder captures:

Wall-clock timestamp (UTC).
Provider, model, request ID.
Input + output token counts.
Cost in cents (derived from a built-in pricing table or MTY_PRICING_OVERRIDE).
End-to-end latency in milliseconds.
The active span / trace ID (if MTY_OBSERVE_OTEL is set).
Any Untaint::after justifications fired on the response.

Reading it back¶

# Default — last 24h, grouped by provider.
mty inspect --cost

# Different window + grouping.
mty inspect --cost --since 7d --by model --top 5

# Drill into a single agent.
mty inspect --cost --by-agent reviewer

# JSON output for piping.
mty inspect --cost --since 24h --json

See reference/cli/mty-inspect.md for the full flag list.

Try it¶

mty check examples/35_observability_demo.mty
MTY_OBSERVE=1 mty run examples/35_observability_demo.mty
mty inspect --cost

The third command should show the demo's recorded mock call.