A few improvements based on code review:
- Don't override existing trace context in `extract_trace_context` - if we're
already in a valid trace (e.g., from HTTP propagation), preserve it rather
than extracting from MCP meta
- Add exception recording to `delegate_span` to match `server_span` pattern
- Remove unused `get_meter` function (metrics not implemented yet)
- Return `None` instead of `{}` from `inject_trace_context` when nothing to inject
- Clean up trivial tests that were just testing OpenTelemetry's own API
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Adds opt-in distributed tracing via OpenTelemetry for observability into
FastMCP server and client operations.
Server spans are created for tool calls, resource reads, and prompt
renders with attributes like component key, component type, provider
type, session ID, and auth context. Client spans wrap outgoing calls
with trace context propagation via W3C headers in request meta.
Components provide their own span attributes through a `get_span_attributes()`
method that subclasses override - this lets LocalProvider, FastMCPProvider,
and ProxyProvider each include relevant context (original names, backend URIs).
To enable: configure an OpenTelemetry SDK with a TracerProvider before
importing fastmcp. Traces export to any OTLP-compatible backend.
Closes ENG-2813
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
