Observability

Every execution runs in a carmy.execution tracing span with these fields:

field	value
execution_id	the execution ID
request_id	the idempotency identity, when present
tool	the tool name
effect	the declared effect
status	completed, failed, cancelled or timed_out
duration_ms	the total duration
replayed	whether the result was replayed
error_code	the error code, on failure

A completion event is logged at INFO on success and at WARN on failure. Arguments and outputs are never recorded, because they may carry secrets.

INFO carmy.execution{execution_id=exec_… request_id="abc" tool=create_order effect="write" status="completed" duration_ms=0 replayed=true}: execution finished

Setup

carmy::run() installs a subscriber that writes to stderr and is filtered by RUST_LOG (default info). Stdout stays free for MCP over stdio.

OpenTelemetry

Carmy doesn’t depend on OpenTelemetry. Compose the layers yourself, and the spans are exported with the same fields:

use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt, EnvFilter};

tracing_subscriber::registry()
    .with(EnvFilter::new("info"))
    .with(carmy::observability::fmt_layer())
    .with(tracing_opentelemetry::layer().with_tracer(tracer))
    .init();

Install your subscriber before calling run(). If a global subscriber already exists, Carmy leaves it in place.