api-telemetry

Overview

The framework auto-instruments every tool, resource, prompt, storage, LLM, speech, and graph call — each gets its own span and the standard counters/histograms. HTTP server requests pick up spans from HttpInstrumentation (all Node.js HTTP traffic, skips /healthz) plus httpInstrumentationMiddleware from @hono/otel on the MCP HTTP endpoint when installed (optional Tier 3 peer — bun add @hono/otel). On Bun, HttpInstrumentation silently no-ops and @hono/otel is the only HTTP coverage. Auth checks and session lifecycle are tracked as metrics only — auth decorates the active HTTP span with attributes, sessions emit counters.

requestId, traceId, and tenantId correlate automatically across spans, metrics, and logs. Pino logs get trace_id/span_id injected when a span is active.

A handler's ctx.traceId / ctx.spanId name the execution span it runs in — tool_execution:<name> or resource_read:<name> — not the enclosing HTTP request span. Under HTTP the trace ID is the request's, so handler logs join to the request; the span ID is the child execution's, so they join to that span's attributes and duration. On stdio, where no transport span exists, both are still populated from the execution span the framework opens. Both are undefined when telemetry is disabled: the non-recording span a disabled pipeline produces carries all-zero IDs, and the framework reports no correlation rather than IDs that correlate to nothing.

For the helper API surface (withSpan, createCounter, createHistogram, buildTraceparent, etc.) — see the api-utils skill, Telemetry section. This skill is the catalog of what is emitted; that one is the reference for how to emit your own.

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Enabling export

OTel is off by default. OTEL_ENABLED=true alone does nothing — you also need an OTLP endpoint. Without an endpoint the SDK is configured but nothing leaves the process.

Env var	Default	Purpose
OTEL_ENABLED	false	Master switch. Must be true to start the SDK.
OTEL_EXPORTER_OTLP_TRACES_ENDPOINT	—	OTLP/HTTP traces endpoint (e.g. http://localhost:4318/v1/traces).
OTEL_EXPORTER_OTLP_METRICS_ENDPOINT	—	OTLP/HTTP metrics endpoint (e.g. http://localhost:4318/v1/metrics).
OTEL_SERVICE_NAME	createApp name → package.json name	service.name resource attribute. Seeded from createApp({ name }) when unset; an env value wins.
OTEL_SERVICE_VERSION	package.json version	service.version resource attribute.
OTEL_TRACES_SAMPLER_ARG	1.0	Trace sampling ratio (0–1) for TraceIdRatioBasedSampler.
OTEL_LOG_LEVEL	INFO	OTel diagnostic logger level (NONE/ERROR/WARN/INFO/DEBUG/VERBOSE/ALL).