OpenTelemetry

The proxy emits OTLP traces, Prometheus metrics, and structured logs. W3C Trace Context is propagated to upstream APIs so distributed traces span your entire stack.

Configuration

telemetry:
  enabled: true
  service_name: mcp-anything
  service_version: 1.0.0

  traces:
    exporter: otlp
    endpoint: https://otel-collector.internal:4318  # OTLP HTTP
    insecure: false
    headers:
      Authorization: Bearer ${OTEL_TOKEN}

  metrics:
    exporter: prometheus
    path: /metrics    # Prometheus scrape endpoint
    port: 9090

Traces

Each MCP tool call produces a trace with spans covering the full request lifecycle:

MCP protocol handling (request parsing, tool lookup)
Auth validation (inbound and outbound)
Request transform (jq expression)
Upstream HTTP call
Response transform (jq expression)

MCP-specific span attributes

Attribute	Description
`mcp.tool.name`	Full tool name (e.g. `kraken__get_ticker`)
`mcp.tool.upstream`	Upstream name
`mcp.transport`	`streamable-http` or `sse`
`http.upstream.url`	URL of the upstream request
`http.upstream.status_code`	HTTP status from upstream

W3C Trace Context propagation

The proxy injects traceparent and tracestate headers into upstream HTTP requests. If the upstream is also instrumented with OTel, traces from the MCP client through to the upstream API appear as a single distributed trace.

Metrics

When the Prometheus exporter is enabled, metrics are available at the configured path:

Metric	Type	Description
`mcp_tool_calls_total`	Counter	Total tool calls by tool name and status
`mcp_tool_call_duration_seconds`	Histogram	Tool call latency distribution
`mcp_upstream_requests_total`	Counter	HTTP requests to upstreams
`mcp_upstream_request_duration_seconds`	Histogram	Upstream HTTP latency
`mcp_active_connections`	Gauge	Active MCP client connections

Trace exporters

Exporter	Description
`otlp`	OTLP over HTTP (default port 4318)
`stdout`	Print traces to stdout (development)
`noop`	Discard all traces

Metric exporters

Exporter	Description
`prometheus`	Prometheus scrape endpoint
`otlp`	Push metrics via OTLP
`stdout`	Print metrics to stdout (development)

Structured logging

The proxy logs via Go's slog package in JSON format. Log level is configurable:

telemetry:
  log_level: info    # debug, info, warn, error

Secret values (tokens, credentials) are never logged. Config fields that reference ${ENV_VAR} secrets show the variable reference, not the expanded value.