api-telemetry

name	api-telemetry
description	Catalog of OpenTelemetry instrumentation built into framework `@cyanheads/mcp-ts-core` — spans, metrics, completion logs, env config, runtime caveats, custom instrumentation patterns, and cardinality rules. Use when enabling OTel export, adding custom spans or metrics in services, debugging missing telemetry, looking up attribute names, or deciding what's safe to put on a metric attribute vs. a span.
metadata	{"author":"cyanheads","version":"1.8","audience":"external","type":"reference"}

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).

Metrics push via PeriodicExportingMetricReader every 15 seconds. Traces use BatchSpanProcessor.

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Runtime support

Runtime	Behavior
Node.js / Bun	Full NodeSDK. Auto-instrumentations: HTTP server (Node http hooks; skips /healthz), Pino logs (trace_id/span_id injection). On the HTTP transport, when OTel is enabled and @hono/otel is installed, httpInstrumentationMiddleware is also wired onto the MCP endpoint — fills the gap on Bun, where the Node http auto-instrumentation silently no-ops. Manual spans, custom metrics, and OTLP export work on Bun regardless.
Cloudflare Workers / V8 isolates	NodeSDK is unavailable. SDK init no-ops silently. createCounter/createHistogram/withSpan calls still work via the global OTel API but produce no output unless you wire a Worker-compatible exporter and ctx.waitUntil() for flush.

Cloud platform detection auto-populates resource attributes:

Detected	Attributes set
Cloudflare Workers	cloud.provider=cloudflare, cloud.platform=cloudflare_workers
AWS Lambda	cloud.provider=aws, cloud.platform=aws_lambda, cloud.region from AWS_REGION
GCP Cloud Run / Functions	cloud.provider=gcp, cloud.platform=gcp_cloud_run (or gcp_cloud_functions), cloud.region from GCP_REGION
All	deployment.environment.name from config.environment

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Flush at exit

Spans batch and metrics push on a 15-second cycle, so a process that exits between cycles takes its telemetry with it. ServerHandle.shutdown() is the drain: it stops the transport, then force-flushes traces and metrics through the OTLP exporters and closes the logger.

Trigger	Path
SIGTERM / SIGINT	shutdown(signal)
uncaughtException / unhandledRejection	shutdown(signal), then process.exit(1)
stdin EOF, stdio transport	shutdown('STDIN_EOF'), then process.exit(0)
ServerHandle.shutdown() called directly	the same drain, no exit

Stdin EOF is a disconnect. A stdio host closing the pipe runs the cleanup a signal runs, exactly once — the shutdown detaches the signal handlers and the EOF watcher as it starts, so neither can re-enter it — and the process then exits explicitly instead of waiting to run out of handles. Two things follow: the OTLP export leaves the process, and a setInterval a service registered without unref() can no longer keep the server resident after its client is gone. The path writes nothing to stdout.

The drain is bounded. Shutdown-on-exit races a 10-second backstop, so a cleanup step that never settles still terminates the process. The logger bounds its own flush separately, per pino instance: a completing callback is awaited in full, and a runtime whose callback never arrives releases shutdown rather than hanging it.

Workers has no ServerHandle and no NodeSDK — flush whatever exporter you wired there yourself, via ctx.waitUntil().

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Spans

Every handler call gets a span. Nested operations (storage, graph, LLM) become child spans on the same trace. All spans carry code.function.name and code.namespace for code-attribution. Errors are recorded via span.recordException() and SpanStatusCode.ERROR; McpError codes surface as the *.error_code attribute.

Span name	Source	Key attributes
tool_execution:<tool>	every tool call	mcp.tool.input_bytes, mcp.tool.output_bytes, mcp.tool.duration_ms, mcp.tool.success, mcp.tool.error_code, mcp.tool.input_required, mcp.tool.partial_success, mcp.tool.batch.{succeeded,failed}_count
resource_read:<resource>	every resource handler	mcp.resource.uri, mcp.resource.mime_type, mcp.resource.size_bytes, mcp.resource.duration_ms, mcp.resource.success, mcp.resource.error_code, mcp.resource.input_required
prompt_generation:<prompt>	every prompt handler	mcp.prompt.input_bytes, mcp.prompt.output_bytes, mcp.prompt.message_count, mcp.prompt.duration_ms, mcp.prompt.success, mcp.prompt.error_code, mcp.prompt.input_required
storage:<op>	StorageService (every call)	mcp.storage.operation, mcp.storage.duration_ms, mcp.storage.success, mcp.storage.key_count (batch ops)
graph:<op>	GraphService (every call)	mcp.graph.operation, mcp.graph.duration_ms, mcp.graph.success
gen_ai.chat_completion	OpenRouter LLM provider	gen_ai.system=openrouter, gen_ai.request.model, gen_ai.request.{max_tokens,temperature,top_p,streaming}, gen_ai.response.model, gen_ai.usage.{input,output,total}_tokens
speech:tts	ElevenLabs provider	mcp.speech.provider, mcp.speech.operation, mcp.speech.input_bytes, mcp.speech.output_bytes, mcp.speech.duration_ms, mcp.speech.success
speech:stt	Whisper provider	same as speech:tts

A handler that ends its round with ctx.requestInput(...) closes its span OK with mcp.*.input_required set — no recorded exception, no error-counter increment. Multi-round-trip input is protocol control flow, so it never inflates error rates; split on that attribute to tell an incomplete round from a completed call.

The measured region

A tool or resource call is measured from the start of the handler through the response pipeline that follows it: output-schema validation, format(), the enrichment merge, and the trailer render for tools; output-schema validation and format() for resources. Telemetry therefore records the outcome the client sees — a failure in any of those is an ERROR span, success=false counters, an error-counter increment, and isSuccess: false in the completion log, matching the isError: true the caller receives. Prompt generation has no post-handler pipeline, so its region is the generate function alone.

Two consequences worth knowing when reading a dashboard:

Signal	What it covers
mcp.tool.duration / mcp.resource.duration	The handler plus validation, formatting, and the enrichment merge — time to produce the result, not time spent in handler code. An expensive format() shows up here.
mcp.tool.output_bytes / mcp.resource.output_bytes	The handler's returned domain value, not the assembled result. content[] re-renders the data the structured payload already carries, so measuring the assembly would double-count it. Nothing is recorded for a call that fails after the handler.

mcp.tool.partial_success and the mcp.tool.batch.* counts read the same domain value, so a batch envelope ({ succeeded, failed }) is still detected once the result has been assembled around it.

Trace context propagates across boundaries via W3C traceparent headers. See api-utils → telemetry/trace for withSpan, buildTraceparent, extractTraceparent, createContextWithParentTrace, injectCurrentContextInto, runInContext signatures.

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Metrics

All custom metrics are namespaced mcp.* (or process.* / http.client.* where standard semconv applies). Lazy-initialized on first emission; tool, resource, prompt, http.client.request.duration, heartbeat, session, auth, rate-limit, and error metrics are eagerly created at startup so series exist from the first export cycle. LLM, speech, graph, and storage instruments are lazy-initialized on first use.

Tools, resources, prompts

Metric	Type	Unit	Attributes
mcp.tool.calls	counter	{calls}	mcp.tool.name, mcp.tool.success
mcp.tool.duration	histogram	ms	mcp.tool.name, mcp.tool.success
mcp.tool.errors	counter	{errors}	mcp.tool.name, mcp.tool.error_category (upstream/server/client)
mcp.tool.input_bytes	histogram	bytes	mcp.tool.name
mcp.tool.output_bytes	histogram	bytes	mcp.tool.name (success only; the handler's returned value)
mcp.tool.param.usage	counter	{uses}	mcp.tool.name, mcp.tool.param (top-level keys supplied by caller)
mcp.resource.reads	counter	{reads}	mcp.resource.name, mcp.resource.success
mcp.resource.duration	histogram	ms	mcp.resource.name, mcp.resource.success
mcp.resource.errors	counter	{errors}	mcp.resource.name
mcp.resource.output_bytes	histogram	bytes	mcp.resource.name (success only; the handler's returned value)
mcp.prompt.generations	counter	{generations}	mcp.prompt.name, mcp.prompt.success
mcp.prompt.duration	histogram	ms	mcp.prompt.name, mcp.prompt.success
mcp.prompt.errors	counter	{errors}	mcp.prompt.name, mcp.prompt.error_category
mcp.prompt.input_bytes	histogram	bytes	mcp.prompt.name
mcp.prompt.output_bytes	histogram	bytes	mcp.prompt.name (success only)
mcp.prompt.message_count	histogram	{messages}	mcp.prompt.name
mcp.requests.active	up/down counter	{requests}	— (in-flight handler executions, all three types)

Storage, LLM, speech, graph

Metric	Type	Unit	Attributes
mcp.storage.operations	counter	{ops}	mcp.storage.operation, mcp.storage.success
mcp.storage.duration	histogram	ms	mcp.storage.operation, mcp.storage.success
mcp.storage.errors	counter	{errors}	mcp.storage.operation
mcp.llm.requests	counter	{requests}	gen_ai.system, gen_ai.request.model